Chevron says four people were killed when a helicopter crashed on the way to an oil facility off the coast of Angola.

A statement by the oil company says the helicopter left Cabinda province on Monday afternoon with five passengers and a pilot. Four of the five passengers were contractors, and the fifth was an employee of Chevron affiliate Cabinda Gulf Oil Co.

The statement says search and rescue efforts began after contact was lost.

Chevron says four bodies have been found, and the search for the other two people continues Tuesday.

Chevron is not releasing the nationalities of the victims.

Angola recently became Africa's leading oil producer as Nigeria struggles with crises including oil militant attacks and a recession.