VIDEOS/PHOTOS: A packed Orange Line train transporting commuters on a bridge that runs over the Mystic River in Somerville caught fire on Thursday morning, sending hundreds of people scrambling for safety. Video shared with Boston 25 News showed flames shooting from a train car and thick smoke billowing into the air. An MBTA spokesman said the train was approaching Assembly Station when it caught fire around 6:45 a.m. About 200 people were forced to evacuate the train, including a woman who jumped into the river and others who climbed through smashed windows. The woman who jumped off the train bridge swam to shore and declined medical attention, according to the MBTA. There were no other injuries reported.