Five workers have been killed in a fire on an oil rig in the Gulf of Mexico, the state oil company Pemex said.

Six people were injured and two others missing, Pemex said in a statement.

The fire broke out on Sunday during planned maintenance work at the Ku-Maloob-Zaap oil production facility, some 100 kilometers from the city of Ciudad del Carmen in southeast Mexico.

The incident was being investigated, Pemex General Director Octavio Romero said in Mexico City.

Operations in the facility’s 125 wells have been suspended, reducing production by 421,000 barrels of crude oil per day, Romero said.

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He ruled out the lack of investment in facilities as the cause of the fire.

Only last month, a gas leak in an underwater pipeline at the Ku-Maloob-Zaap facility caused a sensational fire on the water’s surface.