BRITAIN'S busiest rail route was closed for around an hour tonight after fire broke out on a nearby industrial estate.

Around 100 properties in Darlington were evacuated after the fire spread to an industrial unit which was storing an acetylene cylinder A small fire started in a pile of tyres on Borough Road Industrial Estate, in Darlington, at around 6.45pm and spread to a nearby lock-up.

As they tackled the fire, crews became aware that a gas cylinder was inside the lock-up and set up a 200-metre exclusion zone around the building as a safety precaution with a police cordon on nearby streets.

The exclusion zone included the East Coast Main Line and seven streets in the area, including parts of Borough Road, Middleton Street and Steeplejack Way.

The fire was quickly brought under control and the cordon was lifted at around 8.45pm.

Police and fire investigators were at the scene this evening trying to establish the cause of the blaze.

Andrew Allison, station manager with County Durham and Darlington Fire And Rescue Service, said: "We dont take these decisions lightly because we know they can cause disruption, but if it had gone off while a train was passing it could have been far worse.

"At present the cause of the fire is unknown, but we would suspect it was started deliberately."

A number of train services were re-routed while the cordon was in force, with some reporting delays of around 30 minutes.