Hour-long delays on the Brighton line are expected following the closure of London Victoria due to what was thought to be an unexploded bomb.
The station has now reopened after it was established the "bomb" was in fact a gas cylinder with no danger of explosion.
All trains were suspended from the station after reports of an unexploded Second World War bomb being uncovered close to the station.
But British Transport Police said at 11.25am that the station has reopened and there had never been any danger to the public:
London-bound travellers are advised to find alternative routes.
In a statement Southern Rail said: "We are just receiving reports that due to an incident between London Victoria station and Battersea Park station, London Victoria station has been closed until further notice.
"This means no Southern or Gatwick Express services will call at the station.
"Valid Southern tickets are accepted on London Underground, London Buses, London Overground, Southeastern, First Capital Connect, South West Trains and London Midland services on any reasonable routes.
"First Great Western will accept Southern tickets between Redhill and Guildford. Please allow at least an extra 60 minutes to your journey time."