On Tuesday, Sindri Thor Stefansson is believed to have escaped the low-security prison he was transferred to 10 days prior through a window, according to the Associated Press. He then allegedly traveled 59 miles to Iceland’s international airport in Keflavik, where law enforcement believe he boarded a flight to Sweden, the BBC reported.

“He had an accomplice,” Police Chief Gunnar Schram told Visir, an Icelandic online news outlet. “We are sure of that.”

Police said the plane ticket was in somebody else’s name, according to the AP, adding that he likely didn’t use a passport because he was allegedly traveling to Sweden, which is within Europe’s Schengen area. Though Iceland is not part of the European Union, it is part of the Schengen Agreement, where there is no border patrol.

There is currently an international warrant out for his arrest.

Earlier this year, Stefansson was arrested as a suspect in what Icelandic media have called the “Big Bitcoin Heist,” and according to the Guardian, he is suspected to have been the mastermind behind the operation. In a series of four burglaries — three in December, and one in January — $2 million worth of computers were stolen by a group of 10 people. The computers are still missing.

“This is a grand theft on a scale unseen before,” Reykjanes peninsula police commissioner Olafur Helgi Kjartansson told the AP in March. “Everything points to this being a highly organized crime.”

Iceland has seen an increase in Bitcoin mining due to its renewable energy and cold climate, which are ideal for high-powered servers. So-called “mining” of Bitcoin on high-powered computers takes a large amount of energy. In Iceland, electricity costs are low due to its renewable sources of energy from both geothermal and hydroelectric power plants. Bitcoin mining was set to consume “100 megawatts this year,” according to a February report in the Guardian, which is more energy than most households use.