From dawn, four helicopters circled to drop water in the middle of the burning oil to open a path for firefighters on the ground, noted an AFP journalist.
"Fire crews continue to make their way past the flames so that the brigades in charge of spreading the foam can move forward," explained the governor of Matanzas, Mario Sabines, on his Twitter account.
The thick black smoke released limits the visibility of pilots who are assisted by drones, he said.
“About 40 trucks carrying the dry materials are ready to contain the flames,” added the governor.
On Monday, efforts were concentrated in order to avoid "the spread of fire" at a "terminal where the tanks of clear products" are located, gasoline and other light fuels even more flammable than the crude oil and fuel oil which were in the four tanks consumed, said Alexander Avalos Jorge, Cuba's deputy fire chief, at a press conference.
"The four tanks" of 50 million liters each "were engulfed in flames", he said, "it was a chain reaction".
According to a latest report, a firefighter died and 14 others are missing, 22 people are still hospitalized, including five in critical condition.
The disaster began Friday evening when lightning struck a tank at the depot located in Matanzas, 100 km east of Havana, which contained 26,000 cubic meters of crude oil, or about 50% of its maximum capacity.
Explosions and flames several dozen meters high then spread the fire to the three other tanks containing up to 52 million liters of fuel oil or crude oil.