The derailment occurred on the Washington Metropolitan Area Transit Authority's (WMATA) Blue Line on Tuesday afternoon at about 4:53 pm, between the Rosslyn and Arlington Cemetery stations in northern Virginia.
According to a WMATA spokesperson, no injuries were reported, but passengers were asked to stay on the train for roughly an hour before being directed to walk the 1,900 feet out of the tunnel to safety. The subway system's tunnels contain walkways along one side, opposite the high-voltage third rail used to power the trains, for use in case of emergencies or maintenance.
At least three people required some sort of medical attention, according to local media, including one person who reportedly suffered a panic attack.
Local reporters noted large numbers of fire and rescue vehicles outside the closest WMATA station, located at Arlington National Cemetery. The subway system has a bad reputation for catching on fire.
Several videos appeared on social media more than an hour later, showing emergency personnel directing passengers inside the train on how to escape their rail car, and then later exiting the tunnel.
The situation created a major traffic jam as it forced trains along the Blue Line, which stretches from the city's eastern suburbs in Maryland to Springfield, Virginia, in the southwestern DC suburbs, to come to a halt. However, WMATA tweeted that it was gathering shuttle buses to the area to get commuters moving again.