DETECTIVES investigating an armed raid on a post office in Shotton Colliery are piecing together the movements of the gang's getaway car.

A metallic blue three series BMW was found burnt out in the village of Ludworth, about three miles from the scene of the crime.

Three men wearing balaclavas burst into the post office, in Front Street, immediately after cash had been delivered on Thursday morning.

They brandished a hammer and demanded the money but two female members of staff triggered alarms before diving for cover and the gang fled empty-handed.

As they fled, they were pursued by an off-duty police officer. He was threatened with a hammer and then with a handgun, before the gang made off in the BMW

The false registration plates it was carrying, RJ04 NKL, had been copied from an identical car owned and used by Mill Garages, in Sunderland.

The getaway car, which was only months old, had been stolen from outside a house in Seaham in April.

The original registration plate was YS53 URN.

Four men, arrested at a house, in Ludworth, about an hour after the raid, continue to be held for questioning at police stations in Peterlee and Durham City.

Anyone with information is asked to ring the incident room at Peterlee police station on 0191-586 2621.

Alternatively, they can contact Crimestoppers anonymously on 0800 555111.