BURGLARY gangs are using acid syringes to corrode door locks in a chilling new tactic – sparking an urgent holiday warning.

The criminal crews operating in popular Spanish tourist spots strike during the holiday period, breaking into to steal jewellery and cash.

Three police officers arresting a man on the street.Spanish police making an arrest Credit: Policia Nacional Bags, watches, jewelry, and perfumes seized from burglary gangs by the Spanish National Police.Some of the stolen items Credit: Policia Nacional

Footage obtained from ‘s National shows searches carried out in the towns of Arganda del Rey in Madrid, and ‘s Sagunto.

The video shows officers handling recovered jewellery and watches alongside the tools seized during the raids.

The Policia Nacional said: “Two criminal groups specialised in robberies in homes were dismantled and 32 criminal acts solved.

“Seven arrested, five of them in . Seized jewellery, , and tools.”

The burglars used nitric acid and marked doors with glue thread to detect if there were residents inside, police said.

“They operated throughout the national territory”, the force added.

The first inquiry into the terrifying trend opened in April 2025.

Cops launched a probe into a four-strong gang, two men and two women, operating from safe houses in Arganda del Rey and the capital.

The two women arranged the properties and vehicles, alternating hire cars registered to front men so nothing could be traced back to them.

While one man waited inside a building to watch residents leave, the other kept lookout in the street.

Once a flat was empty they let themselves in using impressioning, a technique that takes an impression of the key and leaves the lock unmarked.

But their scheming ploy was foiled when cops seized the two men moments after a break-in in the city of A Coruna.

The pair were carrying jewellery, cash, door-opening tools and a heavy magnet used to stick the kit under their car to evade roadside checks.

Investigators tied the group to 18 other burglaries across the region.

The two men were remanded in custody and the women were held during house searches that turned up a luxury car.

A second gang, based in Sagunto, injected nitric acid into locks to eat away the internal workings.

After the lock had corroded, the doors could be forced open with basic tools.

Spanish cops said this method has rarely been seen before in the country.

The gang struck at weekends and during holiday periods.

But all three were caught as they prepared fresh raids with a lock already ruined and several flats marked up.

The recent police raids have sparked concern about residents safety, with cops issuing an urgent holiday warning.

Officers advise using well-signposted indoor CCTV, timers on lamps to fake occupancy, and never leaving blinds fully shut.

Police have also urged anyone spotting glue residue or small objects propped against a door to call 091 without touching anything.