Since May 20th, Stockholm police have registered 49 burglaries using acid to melt locks, police spokesman Ola Österling told AFP.

“Then there is likely a number of unrecorded cases. We are waiting for tenants, mainly in central Stockholm, to return from their holidays,” Österling said.

He added that there were no suspects and prior to these cases there was “not a single one in all of Sweden that we are aware of.”

Several forced locks had been analysed and forensic investigators had been able to confirm that nitric acid, a colourless corrosive liquid, had been used.

In an interview with public broadcaster SVT, Monica Krüger of the country’s border police said that criminals “introduce nitric acid… into the cylindrical lock and this acid causes the metal to corrode, which makes it possible to force the lock.”

Although the method used does not make any noise, the acid gives off a strong odour that spreads throughout the stairwell.

Over the past two years, similar burglaries have been reported in Germany, France, Belgium, Austria and Portugal.

“In one of those cases there was a foreign gang that had entered the country, carried out a number of burglaries and then left,” Österling said, adding that Swedish authorities were co-operating with other European police agencies and Europol.

In August 2023, five Georgian citizens were charged in France over a dozen burglaries using acid, also during the summer.