Gov. Mitt Romney seized control Friday of inspections in the Big Dig highway system where a woman was killed by falling concrete, saying an independent assessment was necessary to restore public trust.

Inspectors had already pinpointed at least 242 points where bolts were separating from tunnel ceilings, and their review was continuing.

The Republican governor signed emergency legislation Friday morning that gives him ultimate say on when the tunnels reopens, taking that power away from the Massachusetts Turnpike Authority. State lawmakers had approved the bill Thursday within hours of Romney's request.

After the signing, Romney headed to a meeting with federal and state investigators at the accident site.

"Our effort is going to instead focus on opening the tunnel as quickly as possible and doing so when it's entirely safe," the governor said.

He said he had spoken with the head of the National Transportation Safety Board, as well as criminal investigators, and that they would focus on determining the cause of the ceiling panels' collapse. The state's congressional delegation on Thursday asked the NTSB to lead the investigation, saying it is one of the few agencies without any apparent involvement in the Big Dig.

The eastbound section of the Interstate 90 connector tunnel under South Boston, part of the main route to Logan Airport, has been closed since late Monday, when 12 tons of concrete ceiling panels fell, crushing a car carrying Milena Del Valle, 38, and her husband, Angel Del Valle, 46. He escaped with minor injuries.

Michael Lewis, the Big Dig director, said inspectors found 50 bolt assemblies had come loose in the eastbound section of the tunnel where Milena Del Valle was killed — plus 68 suspect assemblies in the westbound section, 45 in the section carrying carpool traffic, and 79 in ramps connecting Interstate 90 with Interstate 93.

A day earlier, Lewis had only cited 60 potential trouble spots.

He said the road may remain closed for weeks, until federal officials review the panels and workers fix any needing repair, he said.

The panels provided a dropped ceiling for ventilation purposes, but experts have questioned whether they needed to be so heavy — each ceiling panel weighs about 3 tons.

As the tunnel continues to undergo inspections, authorities are considering whether it would be feasible to remove the ceiling panels and leave the large fans above them exposed.

Romney's legislation also provides for a $20 million safety audit of the long-running and troubled $14.6 billion Big Dig project.

Since its start some 15 years ago, the massive highway project that buried the city's antiquated central artery underneath downtown has been plagued by cost overruns, leaks, falling debris and other problems linked to faulty construction.

The state is seeking millions of dollars in compensation from companies that managed the project, and the U.S. attorney's office is also investigating.

Romney, who has been considering a run for president in 2008, has often criticized Turnpike Authority Chairman Matthew Amorello. After the concrete collapse, he threatened legal action to force Amorello to step down.

"When it comes to an issue of inspecting the tunnel system, to have the person who's been responsible for it for the last several years say, 'I'm going to inspect it' and tell us, 'It's now safe,' that's not enough," Romney said.

Amorello told reporters he would accept independent inspections, but he rebuffed requests to resign — even after state lawmakers urged him to accept a lesser role solely as an authority board member.

Romney said the situation with the Big Dig was reaching the boiling point.

"At some point, the pressure builds and builds and builds, and the public gets angry enough, that they say, `You know what? This really is wrong."'