Chunks of material fall from Central Artery tunnel ceiling

Adding a new headache to the trouble-plagued Big Dig, chunks of ''spray-on fireproofing" dislodged last night and fell from a steel girder on the ceiling of the Central Artery's southbound tunnel into a breakdown lane near the Government Center exit, officials said.

The debris, which commuters reported to State Police at about 6:15 p.m., forced officials to close the right lane and breakdown lane for about an hour near Exit 24, said Mariellen Burns, a spokeswoman for the Massachusetts Turnpike Authority, which oversees the Big Dig.

There were no injuries and little effect on traffic, said Burns, who did not know the dimensions of the debris. No impact was expected to this morning's commute, she added.

''We obviously see this as a concern," Burns said. ''Anything that's unexpected is a concern. We want to see what it's about and make sure that it's dealt with."

The $14.6 billion project, which has had repeated cost overruns and delays over its 20-year history, came under intense scrutiny in recent months when outside engineering consultants made public some 700 leaks throughout the tunnels. That revelation came after a breach on Sept. 15 that sent water gushing into the northbound lanes and backed up rush-hour traffic for miles.

Asked whether the falling debris might be linked to the leaks, Burns said, ''I would be completely speculating to say what caused it, but that's what we want to know."

Burns added that taxpayers would not foot the bill for any needed repairs. ''Whoever is responsible will take care of it, just like the leaks," Burns said.

She said officials planned to inspect the southbound tunnel last night to determine where the debris came from, why it fell, and whether the problem is more extensive than what crews found in the right lane. In the coming days, she added, crews also will investigate whether there are similar problems in the northbound lanes.

Since the September breach, the turnpike authority and its management consultant, Bechtel/Parsons Brinckerhoff, have examined about 330 sections of tunnel walls for possible defects. Of those sections, they have found 38 defective panels. The officials also revealed that a leak in January 2004, at the time attributed to temporary construction conditions, resulted from a breached wall.

The inspection last night came at a time officials had planned to close southbound lanes, Burns added.

Globe correspondent Amanda Pinto contributed to this report.