A fire set off by a lightning strike at an oil storage facility raged uncontrolled in the city of Matanzas, where four explosions and flames injured 121 people and left 17 firefighters missing, Cuban authorities said.
Officials said an unidentified body had been found late on Saturday.
Firefighters and other specialists were still trying to quell the blaze on Saturday at the Matanzas Supertanker Base, where the fire began during a thunderstorm on Friday night, the Ministry of Energy and Mines tweeted.
Authorities said about 800 people were evacuated from the Dubrocq neighbourhood, closest to the fire.
The government said it had asked for help from international experts in “friendly countries” with experience in the oil sector.
Deputy Foreign Minister Carlos Fernández de Cossío said the US government had offered technical help to quell the blaze. 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. The first support flights from Mexico and Venezuela were expected to arrive at Matanzas’ airport Saturday night.
The US embassy in Havana said on Twitter: “We want to make clear that US law authorises US entities and organisations to provide disaster relief and response in Cuba.”
The United States has had sanctions against the one-party communist state for six decades.
The official Cuban News Agency said lightning hit one tank, starting a fire, and the blaze later spread to a second tank. As military helicopters flew overhead dropping water on the blaze, a dense column of black smoke billowed from the facility and spread westward more than 100km (62 miles) towards Havana.
Roberto de la Torre, head of fire operations in Matanzas, said firefighters were spraying water on intact tanks, trying to keep them cool in hopes of preventing the fire from spreading.
Cuba’s health minister reported late on Saturday that 121 people were injured, with five of them in critical condition. There were no deaths. The presidency of the republic said the 17 people missing were “firefighters who were in the nearest area trying to prevent the spread”.
The disaster comes at a time when the island – with an outdated energy network and persistent fuel shortages – has faced mounting difficulties in meeting increased energy demands amid the severe summer heat.
Since May, authorities have imposed energy blackouts of up to 12 hours a day in some regions – sparking at least 20 protests around the nation of 11 million people.
According to Cupet, the state oil company, the first tank contained about 26,000 cubic metres of crude, about half its capacity, when it was struck by lightning. The second contained 52,000 cubic metres of fuel oil.
There was no immediate word on how much oil had burned or was in danger at the storage facility, which has eight giant tanks that hold oil used to fuel electricity generating plants.
“I was in the gym when I felt the first explosion. A column of smoke and terrible fire rose through the skies,” resident Adiel Gonzalez told The Associated Press news agency by phone. “The city has a strong smell of sulphur.”
He said some people also decided to leave the Versailles district, which is a little farther from the tank farm than Dubrocq.
Ginelva Hernandez, 33, said she, her husband and three children were asleep when the explosions rang out.
“We threw ourselves out of bed; when we went out to the street, the sky was yellow,” she told the AFP news agency.
“The fear of people on the street is uncontrollable,” she added.
Many ambulances, police and fire engines were seen in the streets of Matanzas, a city with about 140,000 inhabitants that is on Matanzas Bay.
Local meteorologist Elier Pila showed satellite images of the area with a dense plume of black smoke moving from the point of the fire westward and reaching east to Havana.
“That plume can be close to 150 kilometres [93 miles] long,” Pila wrote on his Twitter account.