A smoke incident on Boston’s subway system caused riders to kick out windows and pry apart doors to evacuate a train filling with smoke in a dramatic episode that occurred during the Wednesday afternoon rush hour.

Five people were taken to the hospital for smoke-related injuries, though none were life-threatening, according to the Boston Globe.

Joe Pesaturo, spokesman for the Massachusetts Bay Transportation Authority, said the incident was likely caused by a motor on the train that overheated.

“Passenger safety is the top priority for the MBTA and the authority will conduct a full investigation to determine the cause of the incident,” Pesaturo said.

In videos posted on social media, passengers can be heard coughing and yelling while some climb out of the train’s windows and squeeze through the doorways.

Transit police with flashlights aided riders escaping the train. “Guys, there’s no rush!” they yelled, as people crawled out of windows. “Take your time! Take your time!”

In another video, passengers who evacuated the train and entered the station began to cough even more heavily as they walked up a station stairwell filled with smoke.

Pesaturo said that the train’s operator noticed propulsion issues, called the problem into an MBTA dispatcher, and then walked into the cars to evaluate the situation. When he noticed smoke, he began to alert passengers that they needed to evacuate, and started to manually open doors.

“Doors on the subway remained closed because the train had moved away from the platform.  Doors did not malfunction,” Pesaturo said. “The motor person had begun promptly opening doors to allow passengers to evacuate safely, away from live third rail.”

“Because no announcement had been made on the intercom,” Pesaturo added, “some passengers, understandably, began to self-evacuate through windows.”

The incident occurred at Back Bay station on the MBTA’s Orange Line, which relies on a fleet of railcars that are all at least 32 years old. Those trains are slated to be replaced with brand-new trains scheduled to arrive in 2019.

Riders on the Washington region’s Metro system are familiar with smoke incidents. Most will recall the January 2015 L’Enfant Plaza smoke incident in which a Yellow Line train stalled in a smoke-filled tunnel and became engulfed in noxious fumes. One woman died of smoke inhalation and scores were injured. That incident was caused by an arcing insulator.

Boston’s MBTA is no stranger to such incidents, either. In a situation that occurred that same month on the Red Line, a smoke-filled train caused by a failure in the propulsion system incited panic among riders who kicked out windows in order to escape.

Like Metro, Boston’s MBTA is a transit system struggling with aging infrastructure, outdated trains, frequent service disruptions and financial woes.