The Parrandas festival in Remedios is known for its raucous celebrations and a fireworks contest between two of the town’s neighborhoods.
The Christmas Eve event draws thousands of Cubans and foreign tourists each year.
Cuban state radio says 22 people were burned.
Radio station CMHW reported on its website that the accident left at least two adults in “very delicate” condition.
It also said six children between the ages of 11 and 15 had been hurt, describing their conditions as ranging from serious to critical.
All the victims appeared to be Cuban.
State media did not immediately provide further information.