It has been described as Germany’s most “spectacular” bank heist in years.
On a quiet weekend just after Christmas, a group of thieves broke into a High Street bank in the western town of Gelsenkirchen, by boring through a wall with an industrial drill.
They looted more than 3,000 safe deposit boxes and made off with millions of euros.
Over a month later, police have yet to make an arrest.
For the bank’s clients, some of whom say they have lost their life savings and precious family jewellery and valuables, this is a time of anger, confusion and shock.
There is a strong sense that trust in institutions has been shaken.
The case has thrown up all sorts of difficult questions, and some of them have been spelled out by Herbert Reul, the interior minister in the western state of North Rhine-Westphalia.
Why did no-one notice what was going on? Was it an insider job?
Why did no-one hear the drill and how did the thieves know exactly where the vault was?
Were the bank’s security systems too weak?
Police in Gelsenkirchen are appealing for witnesses to come forward.
Investigators believe the thieves probably broke into the Sparkasse savings bank in Nienhofstrasse through the next-door multi-storey car park in the town’s Buer district.
The thieves may have tampered with an escape door between the car park and the bank, they believe.
Under normal circumstances the door could not be opened from the outside, but the gang managed to make sure it no longer closed properly, allowing them “unhindered access from the car park to the Sparkasse building”.
From there, police believe they overcame several security systems and made their way into an archive room next to the vault, in the bank’s basement.
They set up the drill and bored a hole 40cm (15.7in) wide in the wall leading to the strongroom, where the safe deposit boxes were kept.
The heist must have taken place some time between Saturday 27 and Monday 29 December, according to officials, who think the burglars may almost have been caught shortly before reaching the vault.
Just after 06:00 on 27 December, the fire brigade in Gelsenkirchen and a private security firm received a fire alarm warning from the bank, which may have been triggered by the thieves.
Police and 20 firefighters arrived at the bank at 06:15, “but could not find anything that indicated damage”, police said in a statement.
Graphic showing timeline of heist
The fire alarm had come from the vault, Herbert Reul revealed.
But firefighters could not get in because it was locked with a roll shutter. Reul said they saw “no smoke, no smell of fire, or damage”, so they “concluded it was a false alarm”, which he said was not unusual.
He told a state parliament committee the police did not have the right to search the bank at the time, as it was a matter for the fire brigade. They would have needed a warrant.
Once inside the vault, the thieves opened almost all the 3,250 safe deposit boxes, taking cash, gold and jewellery.
Reul said that computer systems in the bank show that the first box was broken into at 10:45 on 27 December and the last at 14:44. It is not clear whether they managed to open most of the boxes in four hours or if the technology stopped recording data.
Witnesses later told police they saw several men in the stairwell of the car park carrying big bags during the night into 28 December.
Authorities say they do not know exactly how much was taken, but German media estimate the thieves must have got away with up to €100 million (£87m).