A Russian helicopter carrying oil workers has crashed in eastern Siberia, and officials say 10 of the 25 people on board were killed.

Russian news agencies say the Mi-8 helicopter took off from Igarka in the Krasnoyarsk region and crashed 2 kilometers (1.2 miles) away along the banks of the Yenisei River.

It was transporting workers to the remote Vankor oil and gas field, which can be reached only by helicopter or, in winter, by land along the frozen river.

The news agencies quoted prosecutors as saying 10 were killed and 15 injured in Thursday's crash.

Investigators were still trying to determine what caused the crash of the helicopter, which is owned by the local Turukhan air company.

Vankor is operated by the state oil company Rosneft through a subsidiary.