Massive Tracy fire one of largest warehouse blazes in the U.S., officials say

A massive fire that destroyed a huge medical supply warehouse in Tracy - one of the largest blazes of its kind in the country - was still burning Friday as health officials warned residents downwind to avoid potentially toxic smoke.

The fire, reported around 1 p.m. Thursday at 5701 Promontory Parkway, spread rapidly through the roughly 1 million-square-foot Medline facility after firefighters encountered problems with the building's private fire water system, according to the city of Tracy.

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"This is such a unique fire," Tracy Fire Department Chief Randall Bradley said Thursday evening. "A million-square-foot fire is an extremely rare fire in the United States."

Tracy fire officials said Friday evening they have made "tremendous progress" battling the massive warehouse fire, but crews expect to keep working through the night and likely for days as hot spots continue to smolder.

Officials said the cause of the fire remains under investigation by the fire marshal and the Bureau of Alcohol, Tobacco, Firearms and Explosives. They are also still investigating why the building's fire protection systems and yard hydrants had little to no water pressure when crews arrived. A fire official said the fire pump was running, but a gauge showed zero pressure, meaning water was not reaching the sprinkler system or hydrants.

"When we connected to the very first pipe, the very first fire hydrant, there was no water essentially coming out of that hydrant. It was very, very minimal," said Deputy Tracy Fire Chief Brian Bagley.

The building is a total loss, Bagley said, but Medline was able to recover 10 to 15 tractors and trailers carrying various medical supplies and they were decontaminated.

Fire officials said the blaze will take days to fully extinguish.

Mayor Dan Arriola urged residents to monitor air quality through AirNow.gov and to avoid touching debris that may have fallen near homes.

"The city of Tracy is very resilient," Arriola said. "We are so thankful for our law enforcement, fire, public health partners. We know that we'll get through this together."

South San Joaquin County Fire Authority Deputy Chief Brian Bagley said Friday that officials were aware of only a few comparable fires.

"There's been distribution centers that have burned throughout our nation, but to have one, you know, over a million square feet, there's only been two or three that we are aware of, and so it's very, very challenging," Bagley told reporters. "It's a skyscraper laying on its side."

No Medline employees or on-site personnel were reported missing, the company said. Officials said about 120 workers were at the facility when the fire started, out of roughly 900 employees assigned to the site.

No injuries were reported, police said.

The fire began on or near the roof of the warehouse and quickly moved into the building. Bradley said Thursday that "the whole building was engulfed" within about 20 minutes.

Bagley said Friday that the building was fully consumed within about 40 minutes.

Fire officials said high winds, low humidity, heat and the failure of the facility's private fire protection system helped turn the blaze into a major regional emergency.

"We don't know why those fire hydrants weren't pressurized," Bradley said, adding that the facility's fire pumps and alarm systems were last tested in January.

The city said the water problem involved the building's private fire protection system. Municipal water pressure remained stable and continued to support firefighting efforts.

Bagley said Friday that crews had to connect to municipal fire lines about 1,600 feet from the warehouse, requiring two fire engines just to move water close enough to attack the blaze.

Neither of the facility's sprinkler systems appeared to have activated, Bradley said. The cause of the blaze and the apparent failure of the fire suppression systems remained under investigation Friday.

The Bureau of Alcohol, Tobacco, Firearms and Explosives is expected to assist local officials with the investigation. The cause of the fire remained under investigation Friday, and officials said it could be several days before investigators can safely examine the interior of the destroyed warehouse.

The blaze sent a towering column of black smoke over the Tri-Valley and East Bay hills Thursday afternoon. Closer to the fire, county health officials urged residents to stay indoors, close windows and doors, run air conditioning in recirculation mode if available, and avoid strenuous outdoor activity.

San Joaquin County Public Health Officer Dr. Maggie Park said smoke from the fire could pose risks, particularly for children, older adults, pregnant people, and those with asthma, heart disease or other respiratory conditions.

"Among the chemicals that were consumed in the Medline fire were an assortment of respiratory irritants, toxic gases, carcinogens, and at least one neurotoxin," Park said in a statement.

Park said anyone near the smoke plume who developed sudden respiratory problems, headaches, dizziness, nausea or throat irritation should seek emergency medical evaluation.

Several air-monitoring stations had been set up around the incident area, and continuous monitoring showed no protective actions were required as of Friday morning, the fire authority said.

The San Joaquin Valley Air Pollution Control District also warned that smoke from the fire could elevate fine-particle pollution in nearby communities, depending on wind and weather. Residents were advised to monitor conditions through AirNow.gov.

Medline reported last year that the Tracy facility stored bleach, isopropyl alcohol, lye, sulfuric acid and xylene, according to California Environmental Protection Agency records reviewed by the Chronicle. Xylene is a solvent used in some laboratory and medical processes and can be harmful when inhaled.

Fire officials were also reviewing inventory lists for hazardous materials. Bagley said several hundred lithium-battery-powered robots were inside the facility and that burning lithium-ion batteries can produce hydrogen fluoride gas.

The fire's impact extended well beyond the Medline property. Wind-driven embers traveled south, igniting several spot fires in the area. Firefighters battled blazes involving pallet storage areas and several trailers near a FedEx facility.

The exterior of the FedEx building caught fire, but crews were able to prevent flames from engulfing the main facility, authorities said. FedEx said Friday that its building was not damaged and that all employees were safe.

"Our thoughts remain with those affected by this event," FedEx said in a statement. "Safety is our top priority. We are thankful our team members are safe and appreciate the efforts of the local fire department and our safety team."

Additional spot fires broke out near Schulte and Larch roads and near Tracy Municipal Airport. The city said mutual aid crews contained those fires and prevented further spread.

More than 120 firefighters and dozens of pieces of apparatus responded, including crews from San Joaquin County, Alameda County and neighboring jurisdictions. Incident management personnel from Stanislaus County also supported the response.

Medline, based in Illinois, describes itself as a major medical surgical supply company serving hospitals, health systems and other care providers. The company said Friday that the Tracy facility was a local distribution center largely serving parts of Northern California.

"Medline's supply chain is designed with resiliency, scale and flexibility at its core," the company said in a statement. "Immediately following this incident, Medline activated a command center and a network contingency plan and began incorporating secondary and tertiary distribution centers."

The company said product distribution previously handled by the Tracy facility had been reassigned and was being deployed to other facilities in its regional network "to help maintain service and support customer needs."

Fire officials said crews were also working with Medline to move trucks carrying unaffected medical supplies out of the area.

"There's a lot of medical equipment that are loaded up on those trucks that those hospitals and medical facilities are relying upon," Bagley said Friday.

Sutter Health said it was monitoring the situation but did not expect broad impacts.

"Our supply chain teams have contingency plans in place to maintain access to critical supplies," the health system said in a statement.

UC Davis Health said Medline is one of dozens of suppliers it relies on.

"We are a large hospital and that means we have many different suppliers for different things," UC Davis Health said in a statement. "We are asking employees to be careful with supplies until we know the impact of this fire."

Larissa Gomez, a shift supervisor at a nearby Starbucks, said Thursday that workers from nearby facilities walked toward businesses and a rest stop near Interstate 580 after police blocked roads and some employees could not reach their cars.

"There are probably a dozen people - honestly, more than that - sitting in the shade," Gomez said. "I saw a lot of factory workers and FedEx workers walking this way because they weren't able to reach their cars."

The immediate danger to nearby homes appeared limited. Tracy's mayor said the fire was burning in the city's largest industrial zone, away from residential neighborhoods.

Still, officials said the fire scene remained active Friday, with smoke, hot spots and hazardous-materials concerns likely to keep crews there for days.

Fire officials said their primary concern remained embers from the Medline facility and the possibility of other spot fires.

"Although we had a very significant fire, the fact that no firefighters were injured and all employees evacuated quickly is astounding," Bradley said.

Newsroom meteorologist Anthony Edwards contributed to this report.

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This story was originally published June 12, 2026 at 2:07 AM.