Robbers dug a 30-meter (100-foot) tunnel into the safe deposit room of a Berlin bank.

The tunnel led from an underground garage into the bank's safe deposit room, says an AP report, which also noted that the tunnel was "very professional" and must have taken weeks or even months to complete. It was elaborately constructed and even had ceiling supports.

Police were alerted to the break-in early Monday when a security guard noticed smoke coming from the deposit room, the report says.