A Massachusetts Bay Transportation Authority Blue Line train lost power in the tunnel beneath Boston Harbor on Tuesday evening, halting between Aquarium and Maverick stations and stranding roughly 500 passengers. The Boston Fire Department said firefighters needed about an hour to guide riders through three tunnel exits—two in downtown Boston and one in East Boston—using a specialised cart to assist those requiring help. No injuries were reported. Service on the Blue Line had already been disrupted earlier in the day by a medical emergency at Aquarium Station, but trains were running again when a signal failure near the same station triggered the evening breakdown. The MBTA suspended rail service between Government Center and Airport stations, deploying shuttle buses that bypass Bowdoin Station and providing fare-free alternatives on the SL3 bus and the East Boston Ferry, which added extra trips. As of late Tuesday night, trains remained unable to stop at Aquarium while crews investigated the power failure. The MBTA has not given a timetable for full service restoration.