The barrack was meant to be returned to the Westerbork camp as a memorial to the girl who, through her posthumously published diary, became the voice and face of the Jewish genocide in the Netherlands and around the world. Current owner Jan Egges said he rules out "all other possible causes for the fire".

When Egges reached the burning shack on Saturday morning, he noticed that the back of a tractor parked in it was on fire, rather than the front end where the batteries and electronic parts are located. "There was nothing in the structure that could have caused a short-circuit, and there was no stroke of lightning," Egges said.

The police have refrained from making a statement about the fire. Asbestos released in the fire has delayed a police investigation.

The shack made headlines last month, when the Westerbork holocaust memorial centre announced that it would restore barrack no.57 to its original location. Anne Frank and her sister Margot are known to have worked there, removing carbon from old batteries, in August and September 1944, before they were put on one of the last trains from the Dutch transit camp to Auschwitz. Both girls died in Bergen-Belsen concentration camp in the spring of 1945.

The Westerbork barrack was sold in 1957 and relocated to Veendam, where it served as a shack for tools. The memorial centre had tried for years to recover the barrack, but the owner didn't want to return it until the Veendam municipality gave him a permit to build a new shack. In June, the plan to strip down the shed and rebuild it in the camp was finally announced.