The fire broke out between 1.30 and 2 am in a group of government-run warehouses in central Rangoon, Burma's largest city.
About 20 minutes after fire trucks arrived at the scene, four powerful explosions shook the warehouses, killing civilians living in the area and at least five firefighters, police said.
More than 80 people were injured including three or four firefighters who were listed in serious condition, authorities said.
Officials at Yangon General Hospital said they were treating 76 people for injuries, while about five others with superficial injuries were treated and released.
Police said the fire started in Set-San Ward of Yangon's Mingalar Taung Nyunt Township and spread quickly to 41 warehouses containing raw materials for the production of traditional medicines.
All 41 warehouses were either damaged or destroyed as the fire spread to surrounding wooden houses and a Buddhist monastery which collapsed after it caught fire.
"I was sleeping when I felt a big vibration," said area resident Win Htein, 50. "I ran out of my house and saw the warehouses on fire. I fell down and injured my head. Two of my nephews were killed. I saw many others injured."
Five fire trucks also were destroyed by the fire and explosions.
Officials declined to speculate on the cause of the blaze but said many volatile chemicals were stored in the warehouses.