ATTLEBORO (CBS) – Black smoke billowing from a Commuter Rail train Thursday morning was an alarming sight for some riders, but officials say there was never a fire.

Commuter Rail operator Keolis says the 808 train from Providence to Boston had clogged air filters, which caused the dark smoke. No injuries were reported.

Photos and video posted to social media just before 8 a.m. show that some passengers were concerned.

The filters were removed and the train was able to get moving again 20 minutes later.