Thieves have stolen several key artifacts from an exhibition of gold from the ancient kingdom of Dacia at the Drents Museum in Assen, after setting of explosives outside the building.

Among the stolen items is the golden helmet of Cotofenesti, crafted from almost pure gold and dating from 500 BC, along with three gold arm bands.

The heist occurred early Saturday morning, around 3:45 in the morning, when an explosion shattered windows and caused damage to the museum buildings.

Police say several people were involved in what appears to have been a meticulously planned operation. According to the Telegraaf, the thieves were in and out within three minutes.

Interpol has now been called in to assist with the investigation.

Security footage captured several suspects in action, and a burned-out car, believed to have been used by the thieves, was discovered roughly 30 minutes after the explosion.

The police are appealing for eyewitnesses and anyone with dashcam footage to come forward.

Museum chief Harry Tupan said it is a dark day for both the Assen museum and the National History Museum in Bucharest, which had lent the pieces to the exhibition. “Nothing like this has ever happened in our 170 year history,” he said in a statement.

Ernest Oberlander-Tarnoveanu, the Romanian museum director, said that he hopes the items will be brought back safely. “That is my only hope,” he told broadcaster NOS. “They are so important it will be impossible to sell them.”

The exhibition, Dacia – Realm of Gold and Silver, featured more than 50 artifacts from the pre-Roman kingdom and was set to close on Sunday.

Horror

Art detective Arthur Brand, known for his work recovering stolen art, called the theft “a horror.” He said on social media he feared the pieces may never be seen again, given the current price of gold.

Culture minister Eppo Bruins said the Netherlands will do everything it can to recover the items. “These historical artifacts are of great significance to Romania and its cultural heritage,” he said.

Romanian foreign minister Emil Hurezeanu has spoken to his Dutch counterpart, Caspar Veldkamp, “emphasising the exceptional cultural and symbolic significance of the stolen pieces and highlighting the “profound emotional impact this incident generates in Romania,” according to a Romanian government statement.