Though the effort took one month to complete, the gang were caught metres from the store when two of the men came out of a manhole.
The pair were seen carrying two-way radios, reports AFP.
Afterwards, police called in mountain rescue climbers to explore the tunnel and found that it came complete with metal tubing and planks as supports, as well as its own lighting system.
Earlier this month, a different group of thieves in Italy dug a 30-metre tunnel to get to a Naples jewellers, but were arrested by police.
The same store was successfully robbed in January by entering through the sewers.
> Gang dig 100ft tunnel to steal cash machine
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