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,