The TTC is investigating what they call a serious incident after CityNews received exclusive amateur video showing a subway driving with the doors wide open in at least one car.

CityNews viewer Kamal says it was shot just before 6:30 p.m. Friday evening as the train went over the Bloor Viaduct. He claims the door malfunctioned at Castle Frank Station where a TTC employee tried unsuccessfully to fix it. The train later left for Broadview Station with the doors open.

“The crew went and investigated and thought they had resolved the matter clearly because the train then moved off,” said TTC spokesperson Brad Ross. “But as we can see in the video that was not resolved the doors were wide open as it was crossing the viaduct toward Broadview Station.”

@CityNews TTC tried to fix door of a subway Car on line 2. Then TTC let the train go from Castle Franck to Broadview pic.twitter.com/Er0YC7ysr5 — KJ (@NEWSFORWORLD) May 27, 2016

Ross told CityNews, “This is incredibly serious and we will investigate.”

This is not the first incident of malfunctioning subway doors. The TTC issued an apology back in March 2013 after the doors popped open while a train was still in the tunnel approaching Dupont Station. In that incident, a TTC staff member accidently opened the doors.

Later that same week, the doors flew open while a train was moving between Queen and King Stations. Once again, human error was to blame.

Three years earlier, another embarrassing incident. A criminal investigation was launched after a southbound train travelled between Eglinton and St. Clair Stations with the doors wide open. The TTC later determined that the doors had been tampered with.

“If anyone were to ever encounter open doors like that obviously first message is stay away from them, second message is press the emergency alarm yellow strip on the subway train so our crew is aware once they arrive on the next station and can deal with it,” said Ross.