Spanish police have discovered 4,000 Celtic artefacts – almost certainly looted from a nearby archaeological burial site – heaped in empty chocolate and cigar boxes in a building in the eastern town of Illueca.

The builder's owner, believed to be responsible for removing the artefacts from the unprotected site of Aratikos, was released by police but faces charges for what is believed to have been at least 15 years of systematic pillaging. Six metal detectors, belonging to the man, and a ground-penetrating radar (GPR) tool, which can determine if sub-soil has been shifted, were also seized.

Although hundreds of jewels, coins, pieces of pottery and slingshot, all normally found Celtic warrior burial sites, have been recovered two things were notable by their absence: helmets and armour.

However, according to Spanish daily El País, it is likely that the Aratikos site was the source for the small but steady stream of extremely rare bronze Celtic helmets, dating from the 4th century BC – around 18 in total – that started appearing on the market in Germany and Britain in the early 1990s. Such helmets are rarely found complete because they were usually destroyed for ritual reasons. The total value is estimated to be nearly ¤450,000 (£390,000).

Although the pillaging of Aratikos was exceptionally heavy, the looting of such sites has become a regular occurance in Spain.

The Civil Guard, responsible for policing rural areas, reportedly estimates that around 400 archaeological sites are pillaged yearly, 75 per cent of them by thieves using metal detectors.