A criminal gang based in Torrevieja allegedly used a simple thread of glue placed between doors and frames to identify empty homes before carrying out burglaries across Spain.

Now, the Policia Nacional and the Ertzaintza have arrested three suspected members of the group and linked them to around 20 break-ins in the south of Alicante province and the Basque Country.

According to police, the gang used the so-called ‘glue thread’ method to determine whether properties were occupied.

The technique involved placing tiny markers between the door and frame of a property before returning days later to check whether the marker had moved.

If the thread remained intact, the burglars assumed nobody had entered the home and targeted it for robbery.

Investigators say the suspects also selected homes based on the type of lock fitted to the door.

They allegedly used specially adapted master keys with aluminium sheets in a technique known as ‘impressioning’, allowing them to open locks without forcing entry or leaving visible damage.

After entering the properties, the gang reportedly closed doors using only the latch mechanism, making it difficult for neighbours or owners to immediately realise a burglary had taken place.

Police say the group operated with a strict internal hierarchy and took extensive precautions to avoid detection, including the constant use of rental vehicles that were frequently changed to prevent surveillance.

Investigators believe the organisation coordinated its operations from Torrevieja before travelling across Spain to commit burglaries.

The investigation initially involved police stations in Alicante, Elche and Cartagena before expanding after officers detected similar robberies in Bizkaia.

The matching modus operandi prompted the Ertzaintza to join the operation.

Once investigators identified the gang’s alleged operational base, officers obtained judicial authorisation to search the property.

During the raid, police seized jewellery, watches, cash, master keys and specialised burglary tools.

Officers also recovered a large quantity of items believed to be connected to the investigated robberies.

Authorities have linked the suspects to eight burglaries in Alicante, six in Elche, one in Alcoy and five in Bizkaia.

The three detainees have been accused of robbery with force and membership of a criminal organisation.

The case is now being handled by courts in Torrevieja.