JUBA, South Sudan (AP) — A small plane chartered by a Chinese oil company crashed Wednesday in a remote part of South Sudan, killing 20 people, authorities said. One passenger survived.

The flight chartered by Greater Pioneer Operating Co. had 21 people on board, including two pilots, when it crashed while taking off near an oil field in Unity state as it headed to the South Sudanese capital, said the state information minister, Gatwech Bipal.

Local media reports said the passengers were oil company workers. The U.N.-affiliated Radio Miraya, citing the flight manifest, said the victims were mostly South Sudanese, and included one Indian and two Chinese nationals. Authorities did not immediately confirm the identities of the victims.

“We are deeply saddened,” South Sudan's oil minister, Puot Kang Chol, told reporters in the Kenyan capital Nairobi after confirming that 20 people were killed. He was in Nairobi for peace talks aimed at ending South Sudan's cycle of political violence.

It wasn't immediately clear what caused the crash.

South Sudan President Salva Kiir ordered the Transport Ministry to investigate, and said the crash had affected not only the families of the victims “but also the communities, our nation and the entire oil industry.”

South Sudan, which gained independence from Sudan in 2011, is a major oil producer in the region. The East African nation has been trying to ramp up oil production and exports amid persistent cash flow issues for the government.