Rail engineers have said they believe a faulty electrical switch caused a small fire on a passenger train in Lanarkshire.

Three people were treated for smoke inhalation after the blaze which occurred in the middle of a three-carriage Lanark to Milngavie service on Friday evening.

The eight passengers on board were quickly evacuated together with the train crew.

Two men, a passenger and member of staff were taken to Monklands District General Hospital in Airdrie for treatment.

Full investigation

A spokesmen for ScotRail said that all three had been discharged in the early hours of Saturday morning.

The fire service said a woman was also treated at the scene.

The ScotRail spokesman said engineers had spent the night examining the train at Shields depot in the south of Glasgow.

"They are satisfied now that the fire was caused by a defective tap changer, which is the electrical switching device that controls the current being supplied to the motors," he said.

The spokesman added: "We are pleased no-one was hurt, but obviously a full investigation will be carried out into this incident and a report drawn up."

Emergency services raced to Bellshill railway station when they received the report of the fire on the 2122 BST ScotRail service.