Trains running through East Croydon station have been severely disrupted after two "explosions" on the tracks.

Witnesses described hearing a bang and seeing a section of the line burst into flames after train travelled over it shortly before 10.30am.

The fire caused damage to signalling equipment, causing some some Southern and Thameslink trains to be cancelled and others to be delayed or run by an altered route.

Network Rail engineers are at the scene repairing the damage. 

Sam May, who works in the nearby offices dubbed the "50p building", said: "The first explosion was about 10:15am. Went down to have a look and the second one happened just before I turned the corner at 10:30am. 

"Each burst of electricity lasted about 15 secs with loads of smoke."

He added: "The fire wasn’t massive, but the electrical bursts were – could be heard from our office in the 50p building.

"At about 10:40am engineers turned up with fire extinguishers, etc."

Trains between East Croydon and Redhill are being delayed by up to 30 minutes and Gatwick Express has been reduced to a half-hourly service.

A reduced service is running between Brighton and London Victoria.

Southern said trains towards Caterham through Kenley would not call at South Croydon and Purley Oaks. 

A spokeswoman for Network Rail said: "A lineside cable fire has caused some damage to signals. We have got engineers there repairing the damage.

"We have had to thin the service to allow them to get the work done. We hope to have a normal service resumed by peak time this evening."

The cause of the fire is under investigation.

Did you see the explosion? Call the newsdesk on 0208 722 6351 or email chris.baynes@london.newsquest.co.uk