This story was updated at 5:40 p.m.
A dump truck with its bed extended up hit a traffic light and wires for the MBTA's 71 bus this afternoon, requiring traffic to be shut down going through Watertown Square, said Watertown Police.
The truck was westbound on Arsenal Street heading into Watertown Square about 3 p.m. when the the light was hit and the wires were brought down, says Watertown Police Capt. Raymond Dupuis.
The wires fell into the middle of Watertown Square, and carry 600 volts of electricity for the trackless trolley buses, said Watertown Deputy Fire Chief Thomas McManus.
"We hate tying up traffic, but our No. 1 priority is safety for the people working here," McManus said.
Watertown Square reopened at about 5:15 p.m. today for rush hour, with the wires tied up and out of the way. One lane of Arsenal Street heading westbound remains closed as repairs continue on the traffic light.
Some of the wires are still hanging low, and McManus said emergency personnel will have to keep an eye out on them.
The 71 bus is running all the way to Watertown Square again. The MBTA will use diesel buses until the wires are repaired.
Repairs on the light and wires will resume about 8 p.m., Dupuis said. Watertown Square will remain open during the repairs, but some lanes will be closed, he added.