St. Louis, MO (KSDK) - A fire on the outer roof of a Metrolink train late Wednesday has investigators working to determine exactly what caused the blaze.

A witness to the fire contacted NewsChannel 5 around 11:15 p.m. Wednesday, saying the train was on fire near the Delmar station. That same viewer described flames on the roof of the train as passengers were being evacuated.

When our photographer arrived on-scene, police and firefighters were continuing to work the incident and interview people who were riding the train or in the area at the time.

Although no specific cause has been pinpointed, authorities are looking into the possibility of lightning sparking the fire.

The tracks Metro uses were closed in both directions for a time during the investigation, with one side of the tracks being opened shortly afterwards while the disabled train could be removed.

No injuries were reported.