Four people survived and two are unaccounted for after a Russian plane crashed in mountainous northeastern Afghanistan, the air transport agency Rosaviatsia said on Sunday.

The Falcon 10 business jet was believed to be carrying six people on a hospital flight from India to Uzbekistan and Russia before communication was lost on Saturday evening.

“Of the six people on board the aircraft, tentatively, four are alive. They have various injuries. The fate of two people is being clarified,” Rosaviatsia said, citing the Russian embassy in Afghanistan.

The RIA Novosti news agency said two passengers were Russians, one who was seriously ill, and the other her husband who had paid for the flight.

The two-engine plane was built by France’s Dassault in 1978 and owned by a company called Athletic Group and a private individual.

A provincial government official in Afghanistan told AFP the aircraft came down in Badakhshan province, which borders China, Tajikistan and Pakistan.

The area of the crash is eight hours by road from the provincial capital Faizabad, said Zabihullah Amiri, head of the provincial information department.

Russian investigators announced the opening of a probe into the cause of the crash.

The mighty Hindu Kush mountain range cuts through the province, which is home to Afghanistan’s highest peak, Mount Noshaq, at 7,492 metres (24,580 feet) tall.