The state Transportation Department removed 26 loose wall panels from inside the Sumner Tunnel in Boston on Sunday night into Monday morning, out of concern that they might fall onto the road, as one did in the adjacent Callahan Tunnel earlier this month.
Workers conducted "pull tests" on all 2,400 of the metal panels during an inspection, literally tugging on the top and bottom of each one.
"If it moved in the slightest, it was removed," said Sara Lavoie, a spokeswoman for the department.
The Sumner inspection came a week after 117 panels were removed from the Callahan Tunnel, which has 2,800 panels.
The Callahan inspection was conducted after one of the 4-foot-by-9-foot, roughly 100-pound panels fell onto the roadway on Dec. 21. No cars were hit and no one was injured, but the incident tied up traffic in the two-lane tunnel that carries traffic from downtown Boston to Logan International Airport.
The Sumner carries traffic in the opposite direction.
The fasteners that attach the panel to the wall had corroded. Three other nearby panels were also immediately removed.
Conditions are better in the Sumner than the Callahan, which is not surprising, because the Sumner has more recently been refurbished, said Frank DePaola, the state Transportation Department's highway administrator.
"Corrosion ... is something we just have to stay on top of," he said Monday.
The Sumner panels will be replaced in the coming weeks, but it could take longer to replace the Callahan panels.
Officials say they are looking into a lining system that could better stand the test of time, such as fiberglass.
The Callahan will be inspected quarterly and the Sumner twice a year until permanent repairs are made, DePaola said.
The Callahan opened in 1961, but the wall panels were installed about 20 years ago. It is scheduled for a $12 million overhaul in 2014.
The Sumner, which opened in 1931, had its panels replaced several years later.
This program aired on December 31, 2012. The audio for this program is not available.