LONDON, Sept. 15 (Xinhua) -- An explosion in a subway station in west London is being treated as terrorism, British counter terrorism sources told the BCC on Friday.

British counter terrorism police are on the scene of the blast at Parsons Green station shortly after the explosion was reported in on the packed rush-hour carriage at 8:21 a.m. BST (0721 GMT) on Friday.

The blast left commuters with "facial burns" after a "fireball flew down a carriage," witnesses said. Commuters are fleeing Parsons Green subway station as emergency services arrive on the scene.

A number of injuries appeared to have stemmed from a stampede as people tried to leave the station.

The incident created chaos in the area as the subway service was shut down and police stopped people from getting close.