THIEVES who attempted to break into a supermarket cash room by drilling through a weak point in the wall, were put to flight by a police helicopter.

The criminals prised a large stone from the wall at Sainsbury's in Calne, where its cash machines are embedded, on Monday night, before mysteriously disappearing.

The break-in was not reported to Calne police until Tuesday morning, but neighbours say they heard a police helicopter overhead at the time of the incident. Police suspect this may have panicked the thieves.

Sainsbury's said at no point was there any risk of the thieves stealing money from the cash room because all the money is stored in the room's special time-locked vault.

Sainsbury's duty manager Linda Edwards said: "A small person could have squeezed through, but then would have had to break through the room's plaster board second skin and a filing cabinet, but anything beyond that point would have been impossible."

The thieves picked a weak point in the wall at the store, in The Pippin, where a third machine was once positioned. Police suspect the thieves may have used a stonecutter or even a hammer and chisel to remove the 2ft by 3ft stone block, which was approximately 1ft deep.

The incident was discovered on Tuesday when a supermarket employee on his way to work discovered the heavy block on the ground and a hole in the wall.

The store said it was the first time an incident of this type had occurred at the site, but it was due to review some of its security arrangements anyway and the incident will help speed up plans.

Mrs Edwards said the company was also seeking a quote from a stonemason to repair the damage and look into the possibility of strengthening the cash room's second skin.

Investigating police officer Wpc Julie Lewis said: "We would be really interested to hear from anyone who may have seen or heard anything."

Witnesses should ring police on (01249) 812106