BOSTON – The Callahan Tunnel in Boston has reopened after all 2,800 metal wall panels were checked because one of them fell onto the roadway.

The tunnel reopened at about 5 a.m. Monday.

No one was hurt and no cars were damaged when the 4-foot-by-9-foot panel weighing about 100 pounds fell at about 6 p.m. Friday, causing long traffic backups.

State transportation officials say the panel fell because the metal fasteners had corroded.

State workers spent Sunday night and Monday morning physically tugging on the other panels to ensure they were securely in place.

The tunnel was built in the early 1950s, but the wall panels were installed about 20 years ago. The tunnel is scheduled for an overhaul in 2014.