HAVANA (AP) — Cuban firefighters were joined by special teams sent by Mexico and Venezuela on Sunday as they battled for a second day to control a fire blazing at a big oil tank farm in the western province of Matanzas.

The blaze began Friday night when lightning struck a storage tank during a thunder storm, and the fire spread to a second tank early Saturday, triggering a series of explosions, officials have said.

Authorities said Sunday that a body found at the site had been identified as firefighter Juan Carlos Santana, 60. Officials previously said a group of 17 firefighters had gone missing while trying to quell flames, but there was no word if he was one of those.

A total of 122 people had been treated for injuries, including five in critical condition, officials said.

Provincial Gov. Mario Sabines said Sunday that 4,946 people had been evacuated, mostly from the Dubrocq neighborhood, which is next to the Matanzas Supertanker Base in Matanzas city. The facility’s eight huge storage tanks hold oil used to fuel electricity generation.

Dense black smoke billowed up from the tank farm and spread westward more than 100 kilometers (62 miles) to Havana. The Ministry of Science and Technology said Sunday that the cloud contained sulfur dioxide, nitrogen oxide, carbon monoxide and other toxic substances.

The disaster comes as Cuba struggles with a severe economic and energy crisis, with frequent power blackouts hitting during a torrid summer. It was unknown how much fuel had been lost to the flames.

Cuba’s government had appealed for help Saturday from oil nations, and specialized firefighting teams began arriving with their equipment from Mexico and Venezuela late Saturday.

“The support (is) in the prevention of risks and also help to quell the fire by means of cooling based on water and foam,” Mexican Brig. Gen. Juan Bravo said upon arrival. “We hope that more support will arrive soon, such as chemical material.”

Deputy Foreign Minister Carlos Fernández de Cossío said Saturday evening that the U.S. government had offered technical help. On his Twitter account, he said the “proposal is in the hands of specialists for the due coordination.”

Minutes later, President Miguel Díaz-Canel thanked Mexico, Venezuela, Russia, Nicaragua, Argentina and Chile for their offers of help.

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Andrea Rodríguez on Twitter: www.twitter.com/ARodriguezAP