A gang of thieves who spent six months digging a 100ft tunnel under a car park in a bid to raid a shop's cash machine may have only escaped with around £6,000, sources claimed today.

The theft happened some time between 5.30pm on Monday January 2 and Tuesday January 3 at a cash machine at Blockbuster in Fallowfield shopping precinct, Levenshulme, Manchester.

Sources also said today that this was the second time the criminals, dubbed the 'mole gang', had tried to dig their way to the cash machine after an identical plot was foiled in 2007.

It is also believed the gang drilled tiny holes from the roof of their tunnel into the floor of the store, into which they inserted telescopic cameras to see how far along they were.

The thieves dug the tunnel from a railway embankment at the rear of the shop. It went under a car park and beneath the foundations of the store.

The passageway was around 100ft in length and around 4ft tall. It had also been fitted with lighting and roof supports.

The tunnel was dug directly underneath the cash machine, where the raiders used machinery to drill through more than 15 inches of concrete and stole cash from the ATM.

The thieves made their getaway back down the tunnel.

A source at the shopping precinct said: "There was just over £6,000 in the machine. It was only when security came to fill the machine back up that they discovered the hole.

"While they were digging the tunnel they drilled holes through the floor.

"They think they've put telescopic cameras through the holes and into the shop to see how far along they were."

It is understood the shop was closed last Thursday while the building was checked by a structural engineer to make sure it was safe.

The source added: "The last time this happened was in 2007 but they didn't get in. They went down the side of the shop last time and stopped about 3ft short. The roof of the tunnel caved in when they were building the health centre next door."

Police believe the criminals responsible could have spent up to six months digging the passageway.

Detective Sergeant Ian Shore, from Longsight CID, said: "In all my years of service, I have never seen anything quite as elaborate as this.

"These people had obviously spent a long time plotting this crime and I doubt they would have been able to keep their plans secret for all that time, without telling others about their scheme.

"They must also have spent a lot of time in the area over the past few months, which people may have noticed.

"The financial detriment to the victim could have been a lot worse, and the offenders did not get away with as much money as I believe they may have originally hoped. The machine had limited funds available."

He added: "I would ask that anyone who may have noticed anything unusual around this Blockbuster store, or who may have seen or heard anything they think might help us with our investigation, to get in touch."

Anyone with information is asked to call police on 0161 856 4245 or contact the independent charity Crimestoppers anonymously on 0800 555 111.

Blockbuster was unavailable for comment.