In the latest raid, on a house in Bankwood, Appley Bridge, two high performance cars were stolen while the owners slept.
At least six other similar incidents have taken place in the last fortnight.

Officers investigating the crimes in Shevington, Standish and Appley Bridge are warning motorists to hide their car keys when they are at home.

The break-ins have all taken place at night and the car keys have been the main target, although other valuables have been taken on occasions.
In one raid in Chisholm Close, Shevington Moor, overnight on August 26 and 27, intruders took a BMW X5 with a plasma TV in the back.

Half an hour later the same thieves were disturbed at an address in Chisacre Drive, Shevington and fled, leaving the BMW and television behind.

Shevington beat bobby PC Clive Rigby said: "It is worrying that there have been so many incidents of this kind within a short period of time and within a relatively small area.

"Because of advances in technology, the thefts of vehicles can largely be prevented these days if the would-be thieves cannot get their hands on the keys.

"Unfortunately, in most of these recent cases, intruders have been able to do so because the keys, although within a locked house, have been put in obvious places such as on telephone tables by the door.

"It may sound silly but it's much better to take the keys up to bed with you and put them under the pillow or in some other inaccessible place rather than to leave them in more vulnerable places."

Anyone with information on the raids should contact either Standish Police Station on (0161) 856 7183 or Crimestoppers on (0800) 555111.