A fire at an offshore oil platform in the Gulf of Mexico on Wednesday killed at least four workers and sent dozens leaping into the water for safety.
Sixteen workers were reported injured and there may be a number of missing, Mexico's state oil monopoly said. It was not immediately clear whether a significant amount of oil had spilled.
It was the latest disaster that Petroleos Mexicanos, or Pemex, has had to contend with and comes as the struggling company is trying to reposition itself after the government's decision to open the energy sector to foreign investment for the first time in seven decades.
President Enrique Peña Nieto, speaking at an unrelated event, said he had ordered an investigation on the cause of the fire and how to prevent such incidents.
Pemex said eight firefighting vessels were launched to attempt to extinguish the flames, which shot into the air with thick, billowing smoke. The company said it had managed to transport about 300 workers from the oil rig, the Abkatun Permanente, which is in shallow water off the coast of the state of Campeche.
Pemex suffered two major fires and oil spills in the Gulf of Mexico in recent years, including one in 2007 that killed 21 workers. A Pemex gas pipeline explosion killed 26 near the border with the United States in 2012, and in 2013 at least 33 people were killed in a blast at the Pemex headquarters, which was ruled an accident.
The incident considered the worst for Pemex was a 1984 explosion and fire at a gas plant on the outskirts of the capital. The exact toll was never revealed, but at least 500 people were believed killed.
Industry analysts say Pemex has a poor history of maintenance, which company officials say they have been steadily improving. Gangsters also cut pumping lines to siphon off gas or oil, further making the system precarious in places.
Under the energy-sector reform that is Peña Nieto's chief initiative, Pemex will have to improve its performance as private and foreign firms move into the market, analysts say.