Passengers at Birmingham New Street Station were evacuated on Wednesday night after smoke was spotted near the platforms.
The was cleared for 30 minutes shortly after 8pm, as the cause of the smoke from two escalators, which lead to platforms 8 and 9, was investigated.
A spokeswoman for Network Rail said the fire service found it was "smoke without a fire".
The station reopened to the public and no significant knock-on delays were expected. Trains had been passing through without stopping or diverting elsewhere while the station was closed.
Fire crews are still investigating what caused the smoke. No-one was injured during the incident.