Three state senators initiated an independent examination Tuesday into construction of the San Francisco-Oakland Bay Bridge after problems were discovered within Caltrans' testing program.

The request came at the end of a Capitol hearing in which top Transportation Department officials defended the project as exceeding various measures of safety. A Bee investigation revealed that a Caltrans technician who reviewed the Bay Bridge eastern span for safety had falsified test results elsewhere in the state.

The $6.5 billion eastern span, slated to open by Labor Day 2013, is the most expensive public works project in California history. The state is rebuilding the segment as part of a broader program that began after the 1989 Loma Prieta earthquake to ensure bridges can withstand the force of a massive temblor.

A Toll Bridge Seismic Safety Peer Review Panel of four leading engineers concluded in March that the bridge is safe based largely on material provided by Caltrans. But three of them have had financial ties with Caltrans or its contractors in the past. Sen. Mark DeSaulnier, D-Concord, said even if they conducted their work honestly, their connections to Caltrans and holding meetings in private may leave a perception of conflict of interest.

As chairman of the Senate Transportation and Housing Committee, DeSaulnier asked the nonpartisan Legislative Analyst's Office to coordinate an independent panel of experts who can determine whether testing has proved that the Bay Bridge is as safe as Caltrans attests. Two other lawmakers, Sens. Ted Gaines, R-Rocklin, and Joe Simitian, D-Palo Alto, also called for an outside review.

"I don't begrudge Caltrans its passion in defending the work it's done, but we're here to find out for the public what is truly the situation," DeSaulnier said. "And this is complex, because this is a structure unlike any other tried in the world."

Caltrans Director Malcolm Dougherty and bridge engineer Brian Maroney testified that the bridge had passed various tests and was designed to exceed standards for safety. Dougherty condemned Caltrans technician Duane Wiles for falsifying safety test results elsewhere but said the agency had not found such manipulations on the Bay Bridge components that Wiles reviewed.

Simitian suggested that it was odd that Wiles would have chosen to go "straight" on the Bay Bridge while faking other data.

"It seems a little hard to fathom why somebody's work would be without question rigorous in one venue but then problematic in other venues," Simitian said.

Dougherty said he was confident Wiles had not undermined the Bay Bridge project.

"This technician wasn't always working by himself," Dougherty said. "The majority of the time, this technician was working in a team atmosphere."

The Bee previously reported doubts about testing for two of the 13 reinforced concrete piles that make up the foundation of the main tower of the new Bay Bridge. An internal Caltrans report shows that a team of its own engineers recently found data irregularities involving two other piles. Those data are still under review.

Dougherty said he was open to an outside review, though he expressed concern about delaying Caltrans work on the Bay Bridge project.

But Simitian stressed that it was important to ensure the public that the bridge is safe, even if it takes additional time. He said enough problems have surfaced to raise legitimate doubts.

"You don't have the luxury of saying, 'There isn't a safety concern, we have to keep personnel issues closed and, by the way, I don't want to distract us from moving forward,' " Simitian said.

The Federal Highway Administration is conducting a separate review triggered by malfeasance in Caltrans' testing department. A draft report obtained by The Bee said that some of California's federal transportation money could be at risk because the state dragged its feet in notifying FHWA after discovering problems in 2008 and 2009.

But FHWA Division Administrator Vincent Mammano backed off that threat during Tuesday's hearing. He said his office is "completely comfortable" with the subsequent Bay Bridge testing and that he sees "no risk" of California losing federal funds.