The MBTA's general manager said that a decades-old cable led to the shutdown of the Blue Line on Tuesday, which prompted the evacuation of 500 people under Boston Harbor.

The head of the MBTA said more problems were uncovered during an investigation into a Blue Line train evacuation​ that happened on Tuesday.

Around 500 MBTA riders were reportedly stuck on a Blue Line train Tuesday afternoon, according to officials. The train was disabled under the Boston Harbor between Maverick and Aquarium stations, the Boston Fire Department reported. It took firefighters about an hour to evacuate the 500 people through the tunnel.