A helicopter carrying four Americans crashed in Kenya, killing them and the pilot, the Kenyan police said on Monday.

The National Police Service said in a Twitter thread that the helicopter crashed on Sunday evening in Central Island National Park, near the country’s northern border with Ethiopia. It said the cause of the crash had not yet been established.

United States officials confirmed the Americans’ deaths and provided the names of three of the victims — Anders Asher Jesiah Burke, Brandon Howe Stapper and Kyle John Forti — to The Associated Press on Monday.

The police service said the helicopter was one of two that had landed at a “tented camp” on the island, and that the other one had cleared the area safely. The Kenyan news outlet Capital FM Kenya reported early on Monday that the Americans were tourists who had visited the camp and were flying out when the crash occurred.