BOSTON (AP) – State investigators conducting a criminal probe into the Big Dig tunnel ceiling collapse have reconstructed the concrete panels that fell and crushed a car, killing a motorist, and are nearly finished collecting evidence from the accident scene.

Investigators from the office of Attorney General Tom Reilly, who is considering whether involuntary manslaughter charges are warranted, are focusing on how the panels were designed, whether they were secured properly for their weight and if they were tested properly.

Bolts, epoxy glue, anchors, concrete and other materials have been retrieved from the 120-foot area in the Interstate 90 Connector Tunnel where the accident happened July 10, and are being stored and catalogued at a facility off-site, said Reilly spokesman David Guarino.

Another team has reconstructed at a State Police facility away from the accident the ceiling panels that fell and killed 38-year-old Milena Del Valle as she was driving with her husband to Logan International Airport. Del Valle was buried Wednesday in her native Costa Rica.

“It’s much like investigating a plane crash scene. You gather the materials, reconstruct and examine,” Guarino said.

Reilly’s office is also sifting through documents including memos, engineer field reports and contracts obtained by request and subpoena from the designer Gannett Fleming, contractor Modern Continental Construction Co., and project manager Bechtel/Parsons Brinckerhoff.

After last week’s death, Gov. Mitt Romney took over supervision of the repairs and the decision to reopen the two tunnels that were closed for safety reasons. But several federal agencies, as well as Reilly’s office, have launched their own investigations into what happened and whether there were advance warnings of a possible ceiling collapse.

The Big Dig project, the most expensive in U.S. history, buried much of the city’s highway network in tunnels. It took over a decade starting in the early 1990s to complete and has since been plagued by leaks, falling debris, cost overruns, delays and problems linked to faulty construction.

Most investigations related to the ceiling collapse are looking at the epoxy glue used to secure the ceiling panels and their design, as well as whether there were timely inspections, federal and state officials said.

The I-90 Connector Tunnel opened in January 2003. The Massachusetts Turnpike Authority promised bondholders that inspections would take place every three years, with one scheduled to begin in August, according to Michael Swanson, the Turnpike Authority’s chief engineer.

Brian Keeter, a Federal Highway Administration spokesman, said the agency doesn’t inspect construction work.

“We look at the plan that shows, is there a monitoring protocol in place?”‘ Keeter said.

He said it is up to the project owner to make sure that oversight is being carried out.

“The tunnel design consultant, which operates under the auspices of the project management consultant, would put his or her stamp as a professional engineer that industry norms, or industry standards as they apply to the project, are being met,” he said.

Guarino wouldn’t say whether Reilly’s investigators had determined whether proper oversight of the project took place.

“It’s part of our review. We want to know when it was inspected, how and by whom,” he said.

Romney also has called for full disclosure of when inspections took place and has questioned whether there were enough inspections.

Andy Paven, a spokesman for Bechtel/Parsons Brinckerhoff, said, “Like other parties we are gathering facts and we are fully cooperating.”

As the investigations continue, more than 100 engineers and construction workers on Wednesday worked on ways to reinforce all of the ceiling panels in the tunnel where Del Valle was killed. Romney wants the tunnel, an important link to Logan airport, opened as early as next week.

On Wednesday, crews crawled through the ventilation area between ceiling panels identifying the best methods to back up the epoxy fastening system. Romney has declared all the bolts that use epoxy glue in that tunnel to be unreliable and they’re being reinforced with either a steel-to-steel connector or anchor bolts.

“It’s laborious, but we have a presence down there 24 hours a day,” said Jon Carlisle, a spokesman for the Executive Office of Transportation. “Given the impact this had on traffic, they’ve been charged with getting it done as quickly – but as safely – as possible.”

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Associated Press Writer Leslie Miller in Washington contributed to this report.

AP-ES-07-19-06 1804EDT