Cuban army helicopters scrambled to contain a blaze that felled a third tank at a fuel depot on Monday after burning for days, as the search continued for 16 missing firefighters.

According an official update, the confirmed toll from the fire was one person dead, with 24 people receiving treatment in hospital -- five of them in a critical condition. Many others were treated for burn wounds.

The fire on the outskirts of Matanzas, a city of 140,000 people 100 kilometers (60 miles) east of Havana, broke out late Friday after lightning struck one of eight tanks at the depot.

On Monday, the governor of the western Matanzas province said the blaze had spread to a third tank, which collapsed like two others before it.

"The third tank also collapsed, after the second spilled its fuel" as it caved in on Sunday, governor Mario Sabines told state TV.

He said the blaze area was "very big" and the containment effort "very complex."

Aircraft, firefighters and other specialists and equipment arrived in Cuba from Mexico and Venezuela on Sunday after the island nation asked for help from "friendly countries."

Sabines said the teams were preparing an operation to attack the flames with foam, "but this could take a while."

Some 1,900 people had been evacuated from around the disaster site, officials have said.

"Work is intensifying to combat the fire," the Cuban presidency said on Twitter Monday, adding this was a "decisive day" for the effort.

After the first tank caught fire late Friday, the blaze spread to a second tank by the early hours of Saturday.

The first two tanks collapsed overnight Sunday, causing three more reported injuries and spilling their oil.

According to the Cupet state oil company, the first tank had contained about 26,000 cubic meters of crude, about half its capacity.

The second contained 52,000 cubic meters of fuel oil. It was not immediately clear how full the third tank was.

Firefighters had been battling to prevent the third tank from catching fire, dousing it with water to keep it cool, but ultimately to no avail.

The depot supplies the Antonio Guiteras thermoelectric plant, the largest in the communist nation.

The disaster comes at a time the island -- with an outdated energy network and persistent fuel shortages -- has faced mounting difficulties in meeting energy demands.

Since May, authorities have imposed energy blackouts of up to 12 hours a day in some regions -- sparking protests around the Portugal-sized nation of 11 million people.