An MBTA spokesperson said the train operator stopped the train after they spotted a downed wire in the tunnel.

More than 450 MBTA passengers were evacuated from a Blue Line train in the tunnel under the Boston Harbor due to a signal issue Tuesday afternoon.

Hundreds of passengers aboard the Blue Line were evacuated Tuesday afternoon after a train became stuck beneath the Boston Harbor, between the Maverick and Aquarium stations, officials said. Over the course of about an hour, Boston firefighters assisted with the evacuation of 500 people from the disabled train, the department said.