Officials initially said the explosion was caused by a fire at a construction site in Melones.
Thirteen Cuban soldiers are missing after an explosion at an ammunition depot. The arsenal contained arms and ammunition.
The explosion shook the small rural town of Malones in eastern Holgin province on Tuesday morning, Cuba’s armed forces said overnight.
The Melones area is 724 kilometers southeast of the capital, Havana. Officials earlier said the explosion was caused by a fire at a construction site.
Authorities said they were investigating how the explosion occurred.
The Cuban military said four officers and nine soldiers were among the missing.
Videos on social media showed flames and plumes of black smoke billowing over a row of dense trees near Malones.
Firefighters and rescue teams are working to extinguish the fire. Local police and soldiers are guarding the roads leading to the scene.
On Tuesday, officials said 361 people had been evacuated after the blast.