PORTLAND — An excavator being used to work on Interstate 295 in Portland was headed south in the northbound breakdown lane when its boom snagged utility lines at Washburn Street, snapped a pole and shut down the state’s busiest stretch of highway for five hours Friday morning.

The lines were fiber optic cables, not power lines, but Maine State Police determined that motorists’ safety required that the highway be shut down as the wires draped on the excavator. The incident occurred at 1 a.m. and the road did not fully reopen until 6:21 a.m., said Sgt. Robert Burke, state police supervisor.

State police, Portland police and Maine Department of Transportation crews blocked the highway in both directions. A number of cars and trucks had to be backed up on I-295 northbound and then taken off the highway using on-ramps because there was no room to turn around, Burke said.

“We had probably 30 to 40 vehicles stuck in the northbound lanes,” he said. The tractor-trailer had to be backed up to the exit 5 on-ramp where the interstate crosses Congress Street, he said. 

Central Maine Power Co. was summoned to replace the pole and Time Warner and Oxford Networks worked to restore tension to the lines to get them off the road, he said.

Traffic was relatively light at 1 a.m. but the magnitude of the operation meant all the troopers working in the area had to help divert traffic, which detoured using the Congress Street and Forest Avenue ramps, he said. The incident slowed the early morning commute but the highway was opened before the bulk of the morning commuter traffic started flowing.

State police spokesman Steve McCausland said there may still be delays intermittently Friday as crews continue to work on the lines.