The station was evacuated last month too after a fire under a Gatwick Express train.
There is currently no service on the Victoria Line between Warren Street and Brixton. Check TfL's website for real-time service updates.
Update: the station has now re-opened and the line is running again, but with severe delays. LFB say no fire was found.
Photo by murphster_uk in the Londonist Flickr pool.