MEXICO CITY (AP) — Mexico’s state-owned oil company says one worker died when a gas leak caught fire and shout out flames at a refinery in the northern state of Tamaulipas.

Petroleos Mexicanos, known as Pemex, said the blast Friday also injured 11 workers at the refinery in Ciudad Madero.

The company said the blast happened at a coker plant that wasn’t operating because of maintenance work being carried out at the time of the accident. The blast didn’t start a bigger fire and the installations were not damaged.

Pemex said experts will investigate what caused the accident.

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