The company that provided the epoxy blamed in the fatal Big Dig tunnel collapse was indicted Wednesday in the death of a motorist crushed by ceiling panels.

Powers Fasteners Inc., was charged with one count of involuntary manslaughter, Attorney General Martha Coakley said. The Brewster, N.Y.-based firm was the only company involved in the construction and design of the tunnel to be indicted by the Suffolk County grand jury, Coakley said.

A report from the National Transportation Safety Board released last month found the July 10, 2006, collapse could have been avoided if designers and construction crews had considered that the epoxy holding support anchors for the panels could slowly pull away over time.

Milena Del Valle, 39, was killed when 26 tons of concrete panels and hardware came crashing down from a tunnel ceiling onto her car as she and her husband drove through the westbound I-90 connector tunnel. Her husband crawled out of the rubble with minor injuries.

Prosecutors said Powers Fasteners knew the type of epoxy it marketed and sold for the nearly $15 billion project was unsuitable for the weight it would have to hold, but never told project managers.

"They failed to make that distinction clear," said Paul Ware, hired as a special investigator by Coakley.

The company did not immediately return a call seeking comment.

The maximum penalty for a company charged with manslaughter in Massachusetts is $1,000. Coakley said there may need to be changes in the law, saying the criminal statute may be "wholly inadequate."

The indictment comes after more than a year of investigations by state and federal agencies, which Coakley stressed are continuing. The charge does not directly affect a separate wrongful death lawsuit that Del Valle's husband and daughter filed against Powers, the Massachusetts Turnpike Authority and eight other companies.

Jeffrey Denner, an attorney for Angel Del Valle, said he believes the grand jury would continue to consider criminal charges against others involved but that it was appropriate to charge Powers.

"They are certainly as culpable as it gets. They are the people who supplied the epoxy," he said.

In the report released last month, federal investigators spread blame for the collapse among the many corporations, consultants and engineers involved in the Big Dig project, the most expensive highway project in U.S. history. The agency also faulted the Massachusetts Turnpike Authority for failing to conduct a timely tunnel inspection program.

The NTSB singled out Powers for providing "inadequate and misleading" information about its Power-Fast epoxy. Tests had shown the epoxy's "Fast Set" formulation to be "subject to creep under sustained tension loading," the report said.

Officials from Powers Fasteners said after the report was issued that it would be "an absurd conclusion if the federal investigators were to consider Powers Fasteners in any way responsible, since the overwhelming evidence is that the fault lies elsewhere."

Del Valle's death prompted tunnel and road closures and sparked a public furor over the Big Dig. The project, which had an initial price tag of $2.6 billion, has been plagued by problems and cost overruns throughout the two decades it took to design and build.

The construction buried the old elevated Central Artery that ran through the heart of Boston with a series of tunnels, ramps and bridges.