BOSTON -- Project managers for the Big Dig are doing what they can to put out the fire over loose fireproofing material.

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Earlier this week, NewsCenter 5's Jack Harper reported, a chunck of fireproofing material fell on the southbound side of the Interstate 93 tunnel. Inspectors immediately started looking for more loose material.

Officials said Thursday that most of the problems were found above maintenance walkways along the tunnel walls.

"We are about 90 percent done with those inspections, and what we have found is that there are about 20 areas total that look to have some issues -- maybe not as substantial as the larger piece that came down on Monday night. And again, it is tough to tell if that came down in a chunk or if it came down in smaller chunks," said Big Dig spokeswoman Mariellen Burns.

Permanent repairs to the fireproofing are scheduled next summer, when repairs to the leaks plaguing the tunnel will also be fixed.

Motorists driving along I-93 will see some changes this weekend when all the southbound lanes open to traffic. Officials said the lane openings should ease rush hour congestion considerably. The I-93 high occupancy vehicle lane, or carpool lane, will extend over the Zakim Bridge into the tunnel.

"By Saturday morning, I-93 mainline traffic, three lanes of I-93 mainline, will be going straight through on the left side," said Project Director Mike Lewis.

Other changes include a new on ramp at Congress and Purchase streets, an improved exit 20 leading to the Massachusetts Turnpike and three full through lanes on I-93 south past exit 20.

"So I-93 will have one lane that will continue on to the Mass Pike, and the second lane will come in from the local on ramp. That will help drain the financial district in the evening" said Lewis.

Officials say up to 9,000 cars a day should use the Congress Street exit.