STORY: Cuban state-run television said at least 49 people were injured in the second blast. Civilians had already been evacuated from the area.
According to the Health Ministry, of those injured, one was critical and seven others were in a "grave" condition.
President Miguel Diaz-Canel visited the scene 80 miles east of Havana around midnight and returned during the morning as state-run television broadcast live coverage of the unfolding disaster.
Diaz-Canel tweeted before the second blast that first responders were "trying to avert the spread of the flames and any spill of fuel" into the Matanzas bay.
By Saturday morning, the fire appeared completely out of control, threatening other nearby fuel storage tanks.