Norwegian police on Sunday said they were investigating the disappearance of WikiLeaks founder Julian Assange's associate Arjen Kamphuis, a cyber security expert, who was last seen in northern Norway.
"We have started an investigation," police spokesman Tommy Bech told AFP, adding that so far they had no clue about the Dutch citizen's whereabouts.
The police "would not speculate about what may have happened to him," Bech said.
WikiLeaks tweeted on Saturday about Kamphuis's "strange disappearance", saying he had been missing since August 20 when he left his hotel in the northern Norwegian town of Bodo.
It added that Kamphuis had a ticket for a flight departing on August 22 from Trondheim, a city located more than 700 kilometres (435 miles) south of Bodo.
"The train between the two takes (approximately) 10 hours," suggesting he disappeared either in Bodo, Trondheim or on the train, WikiLeaks said, triggering numerous conspiracy theories on Twitter.
Assange has been holed up at Ecuador's embassy in London since 2012 when he was granted political asylum as he feared extradition to the United States to face trial over WikiLeaks' publication of secret US military documents and diplomatic cables in 2010.