Several of the thieves who stole one of Romania’s most important national treasures from the Drents Museum in Assen are from Noord-Holland province, police have said, as the investigation into the heist continues.

The car used by the robbers was stolen in Alkmaar and there are other “interesting leads” that point to the province, police said.

On Tuesday evening, the police used television crime show Opsporing Verzocht to  ask for information about discarded tools and items of clothing, and a hammer found in a nearby pond.

The heist occurred at around 3.25 on Saturday morning after an explosion shattered windows and caused damage to the museum buildings. The thieves made off with the golden helmet of Cotofenesti, crafted from almost pure gold and dating from 500 BC, along with three gold arm bands.

The Romanian authorities have since criticised the Drents Museum for not having enough security measures in place. Camera footage of the heist shows three men breaking down the door following the explosion.

The director of the National History Museum in Bucharest, which lent the items to the Drents Museum, has also been fired amid an investigation into the export licence for the artifacts.

At a press conference on Tuesday, Romanian prime minister Marcel Ciolacu said no such licence had been issued for the the transport of the objects to the Netherlands.

He also said Romania would “claim unprecedented damages” for the loss of the helmet. The Dutch culture ministry has not received a claim yet, a spokesman told the AD.

“We are in contact with the Romanian authorities and working closely together,” he said.