The train, with up to 70 passengers aboard, was surrounded by police just outside Kidderminster station in Hereford and Worcester. The train was stopped after a witness reported seeing a man who robbed the Leeds building society in Worcester with a handgun board a train for Birmingham.
A West Mercia police helicopter followed the train which was halted outside Kidderminster. British Rail told passengers the train had stopped because of a mechanical failure.
After a delay of more than an hour, the train entered the station. But police told passengers over the tannoy system to remain sitting on the train. An officer read out a description of the wanted man and asked anyone fitting the description to leave the train.
A police spokesman said one man, apparently fed up with the delay did disembark, but was ruled out of their inquiries.
A man fitting the police description did get off after a second message was read out. He was arrested and taken to Kidderminster police station where detectives from Worcester planned to interview him.
The train was being searched, but last night no weapon had been found.