BOSTON (AP) – Federal prosecutors have been gathering information about leaks in the Big Dig tunnels, a published report said Thursday, two days after the state attorney general said he’s investigating two of the largest contractors on the $14.6 billion highway project.

Prosecutors in U.S. Attorney Michael Sullivan’s office met twice, including three weeks ago, with retired Judge Edward M. Ginsburg, who until last month oversaw cost-recovery efforts from contractors.

Ginsburg told The Boston Globe that the prosecutors asked about the cause and extent of leaks in the Interstate 93 tunnels. The prosecutors were interested in whether key documents related to the construction history of the tunnels were missing.

“The were interested in missing documents,” he said.

Sullivan spokeswoman Samantha Martin declined to comment.

The federal and state inquiries come amid new questions about the project’s safety.

Attorney General Thomas Reilly, who last month took over the cost-recovery effort, said his civil investigation into Bechtel/Parsons Brinckerhoff and Modern Continental Construction Co. focuses on what he called poor oversight and shoddy work on the project, a system of bridges and tunnels plagued by cost overruns and riddled by leaks and other flaws.

Engineer Jack K. Lemley, who led an independent investigation into leaks, said in a March 9 letter to the Massachusetts Turnpike Authority, which oversees the Big Dig, that he can no longer vouch for the safety of its tunnels.

Gov. Mitt Romney responded by asking the state Supreme Judicial Court for an opinion on whether he can fire Turnpike Chairman Matthew Amorello.

House Speaker Salvatore DiMasi said Thursday that he’ll wait to see the outcome of Reilly’s investigation before taking a position on Amorello’s future.

“The attorney general is in there,” DiMasi told a breakfast meeting of the Greater Boston Chamber of Commerce. “I have confidence in him, and until I hear anything different about what is going on … I don’t see any reason why Matt Amorello should resign.”

Amorello insists the tunnels are safe, and says he has “no intention of resigning.” He said Lemley no longer works on the project, and doesn’t have access to information. He said any information requested by Reilly would be provided.

Meanwhile, Lemley may rejoin the effort. The state Highway Department has asked if he would consider returning, and Reilly said on Wednesday that his office has reached out to Lemley, as well. Lemley has not publicly responded.

The tunnels are the centerpiece of the massive highway project, which buried Interstate 93 under downtown Boston and connected the Massachusetts Turnpike to Logan International Airport.

The $14.6 billion highway project has been plagued for years by cost overruns and management problems. In September, water broke though a faulty wall panel and flooded the I-93 northbound tunnel, backing up rush-hour traffic for miles. A subsequent investigation headed by Lemley found hundreds of smaller leaks.