The Royal Mail is reviewing security after two North Yorkshire post offices were targeted on the same day.
A gang of men used a chainsaw to break into Helmsley Post Office at about 5.15pm on Tuesday.
Earlier that day, at about 1.20am, three men fled empty-handed from Hovingham Post Office, and police say the two incidents may be connected.
Royal Mail spokesman Sean Edmunds said: "With any such robbery we would always review security. We would simply warn sub postmasters in the region to be extra vigilant."
Detective Sergeant Fieldsend, of Malton CID, is heading the inquiry into the vicious attack at Helmsley which left postmaster Geoff Simpson needing hospital treatment.
Mr Simpson suffered an injured nose, badly-bruised ribs, sore eyes from some form of spray used to stun him, and a badly-hurt shin where the thieves had stamped on him.
The postmaster told police he had locked the back door when he heard a loud bang and then a chainsaw started cutting through the door. Three masked men pushed in and straight away sprayed him in the face, punching him to the ground and kicking him.
A female assistant was also treated at the Friarage Hospital in Northallerton for the effects of the spray.
Officers said one man was about 6ft 2in and broad, with the other two slightly shorter. They are looking for a man who was seen near the rear entrance to the post office at lunchtime that day. He is described as white, in his 40s or 50s, with wavy brown hair and a bushy moustache. He was slim and around 5ft 9in. They are also interested in tracing a dirty late model Ford Mondeo, seen just after 9am that morning at the junction of Station Road and Ashdale Road about half a mile away from Helmsley Post Office.
Three men were in the car and police would like them to come forward so they can be eliminated from inquiries.
Officers are also keen to learn where a length of wood similar to a gate post, which was left at the scene, may have come from. A gas cylinder was also discarded by the gang. Anyone with information is asked to contact the Ryedale Witness Line on 01723 509662.
Updated: 11:12 Thursday, January 16, 2003
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