Wednesday update: With all precincts reporting, Measure B had received 72% of the vote to easily pass the two-thirds approval needed to pass.

Librarian Laurel Prysiazny said, "Once again, the public has invested in Fresno County libraries through their votes. We are extremely grateful for their confidence in our efforts to use Measure B funds wisely and prudently to date. Their vote of confidence proves that communities value the library more than ever during these tough economic times."

The sales tax credited with making Fresno County libraries the envy of the Valley appeared to be headed for an extension in early returns Tuesday night.

With almost a third of the vote counted, 72% of the ballots were in favor of Measure B, which would extend the one-eighth-cent library tax another 16 years after its March expiration.

The measure needs a two-thirds vote to pass.

Measure B accounts for roughly half the library system's budget, paying for books, librarians and remodels at 36 libraries. The measure, perhaps most notably, financed construction of the crown-jewel Woodward Park Regional Branch in 2004.

Losing the sales tax would have a crippling effect on the library system.

"I'm optimistic," said county Librarian Laurel Prysiazny, who was attending a Measure B open house in north Fresno on Tuesday night. "We've been cautiously optimistic all along."

Still, library officials have prepared contingency plans, should the measure fail, that include closing half the system's branches and laying off 154 of 292 employees.

But victory would be sweet for library officials who have recently made deep cuts to the system due to the weak county budget and still are fretting the loss of a similar tax extension four years ago.

Since its passage in 1998, Measure B has raised close to $150 million.

The money has fueled an unprecedented expansion of the library system that now claims 295,000 card holders and more than 2 million books, CDs and other materials.

"When other counties were shutting down libraries, we were building new libraries," said county Supervisor Susan Anderson, who helped campaign for the tax extension. "I think our library system is superior to most counties in the state."

Measure B had enjoyed broad support going into the election, according to limited polling. Pro-library signs were among the most common political beacons in Fresno County over the past few months.

But with the high two-thirds threshold needed for approval and general apprehension about taxes, the fate of the library tax was anyone's guess.