Some €4 million worth of precious metals is missing after a robbery from an armoured vehicle in Amsterdam in May, Dutch media report.

The robbery turned into a high speed chase leading to six men arrested and one shot dead by police. The van apparently made a weekly delivery of material including gold to a smelters for reprocessing.

At the time, it was believed that all precious metal had been recovered, but NU.nl reports that an investigation by Schöne Edelmetaal, where the robbery happened, and transport firm Brink’s, has found that €4.2 million worth of materials is missing.

The goods, thought to be platinum and gold, came from Germany and Belgium. The total value of the transport is thought to have been tens of millions of euros, according to the AD.

On Wednesday, six suspects will appear before a court in Amsterdam. Another three are still thought to be on the run.