An e-cigarette is believed to have caused a small explosion at London Euston station, but no-one was injured, police said.
The station was closed for about 90 minutes while British Transport Police (BTP) investigated. London Underground trains did not stop at the station.
Police were called at about 19:40 BST.
Network Rail advised there would be major disruption until the end of the day. It urged passengers to go to other stations to get to their destinations.
Euston Road was closed in both directions between Judd Street and Melton Street and has since reopened.
On social media people described how crowds ran from the scene. (BBCNEWS)