A congressional committee is investigating California's $68 billion high-speed rail project. The U.S. Government Accountability Office is investigating, too.

Meanwhile, this proposal for the largest public works project in California history is the target of a flurry of lawsuits filed by local governments and opposition groups.

All those investigators, lawyers and bullet-train critics want to pore over the California High-Speed Rail Authority's trove of documents, looking for evidence.

So it's an unusual time to purge five years' worth of project emails, critics say. Nevertheless, that is what the agency is contemplating.

In February, the rail authority filed papers with the state saying it intended to enact a new policy to destroy its emails after 90 days.

Then, on May 1, in response to a request for information from a project critic, the rail authority said it could not produce emails that were older than 90 days, citing the new policy.

The rail authority's lawyer downplayed the issue's significance, but it has caused concern among high-speed rail critics, who say they fear the authority is jettisoning important information about how the expensive project is being shaped.

The new email policy is "highly suspect," said Kathy Hamilton of the Community Coalition on High Speed Rail, a San Francisco Peninsula group that opposes the bullet train. The project would link San Francisco and Los Angeles with trains traveling up to 220 mph.

It was in a letter to Hamilton that the rail authority first revealed its new email policy.

In a phone interview, Hamilton said she didn't believe the rail authority had already discarded the emails she sought -- exchanges between the staff and a panel of rail experts called the peer review group. In the past, the group has criticized the rail plan's financial projections.

"If they are being investigated and they have been dumping emails, they would be in all kinds of trouble," Hamilton said of the rail authority. She said she had forwarded the letter about the email policy to the staff of U.S. Rep. Darrell Issa, a Republican from Vista and chairman of the House Committee on Oversight and Government Reform.

Issa's committee is investigating alleged misspending of federal funds on the rail project. In a letter last month, the lawmaker warned the rail authority to preserve two years' worth of documents, including emails, so his investigators could review them.

In a phone interview, Thomas Fellenz, chief counsel and acting chief executive officer for the rail authority, said the emails sought by Issa have not been discarded.

Fellenz said all state agencies are supposed to have a policy on retaining documents, including emails. But the rail authority had never enacted a policy regarding email, he said.

Most state agencies delete emails after 90 days, he said. The rail authority's staff will cull the email, saving documents that "we think, for business or legal reasons, we need to retain" and dumping the rest, he said. There is a five-year backlog. But nothing will be discarded until after Issa's probe is complete, he said.

"We will be completely responsive to the committee," he said. "We stayed our implementation [of deleting e-mails] -- we have this investigation ongoing."

Fellenz acknowledged that the rail authority does indeed have the emails Hamilton had sought in her request, which she made under terms of the state Public Records Act. The authority has sent her another letter saying it would give her the emails she requested, he said.