Bomb squad officers have been consulted by police after an explosion blasted open the doors of the post box outside Pewsey Post Office late on Friday.

There was a second mysterious incident at the same time that caused smoke to billow from a bottle bank near the village's Co-op supermarket.

Residents living near the Co-op told firefighters they heard a small explosion.

Police believe both incidents were the work of vandals.

They occurred at about 10.45pm when a large number of young people were milling about in the centre of the village.

Police have previously expressed concern about young people travelling into Pewsey at weekends from a wide area and being involved in vandalism or criminal damage.

Officers tried to play down the incidents on Friday night fearing copycat incidents that could result in injuries either to the pranksters or to passers-by or neighbouring residents.

Officers avoided the word explosion but it was evident that some form of explosive device was placed in the post box.

An engineer carrying out repairs to the shattered locking mechanism on the pillar box on Monday pointed out that a thick steel container into which the mail drops had been twisted out of shape.

The engineer said he doubted if a firework could have caused such damage and said: "It looks as if it was a bomb."

The post office explosion was sufficiently loud for retired health worker Jane Winkley, who lives on the opposite side of North Street, to think she had heard a gun going off.

Mrs Winkley said the sound made her window rattle and there was a loud bang rather as if a bird had flown into the glass.

Firefighters called to the post office found letters strewn about the forecourt.

Some of the mail been singed by the blast but none was burned indicating it was unlikely a flammable substance had been poured into the mail box.

Police sources said they suspected a thunderflash, a military training device that causes a flash and a small explosion, might have caused the damage. An alternative possibility, they said, was that vandals had got hold of explosive rook scarers used by farmers.

While the firefighters were at the post office examining the damaged mailbox, a member of public told them that smoke was billowing from a bottle bank near the Co-op.

The firefighters went to the recycling centre, where there are also paper and fabric banks, and saw smoke coming from the steel bottle container.

Fearing there could be another explosive device inside they kept their distance and cordoned off the area.

Police summoned a bomb squad team from Tidworth and their own crimes scenes investigators were called and collected forensic evidence from the post box.

The bottle skip was later taken to the recycling centre at Compton Bassett where police carried out a detailed search but could find nothing that would have caused the smoke. There was no evidence from the labels on bottles and jars that there had been any fire in the container.

Similarly no evidence was found in the post box identifying what caused the explosion.

One police source said: "We are seeking expert advice on whether there is anything left when a thunderflash goes off."

Police spokesman for the Salisbury division Dave Taylor said there were fears that publicity might encourage carbon-copy incidents.

He said a detailed examination had been carried out on the contents of the post box. "Inside the box we found nothing, it is a mystery," he said.

Police have advised people who put mail in the post box on Friday evening that it has all been retained for forensic tests and that any urgent correspondence, particularly things like credit card payments, should be sent again.

Police would also like to hear from anyone who saw suspicious behaviour near the post box or bottle bank between 10.30 and 10.45pm on Friday.

Any information should be passed to PC Billie Johnson at Pewsey police station on (01672) 562222.