The head of the MBTA said more problems were uncovered during an investigation into a Blue Line train evacuation that happened on Tuesday in Boston and he vowed that the agency will work to fix them.Passengers were forced to walk through a dark tunnel in sweltering heat and humidity after the Blue Line train broke down.

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.