The blast occurred in Mingalar Taung Nyunt, a mainly residential area about a 15 minute-drive from central Yangon, the country's former capital. It struck a compound of warehouses that the government rents out to private businesses.
"I can't tell what is the exact cause of the incident but it is unlikely from man-made bombs," said a police official, who declined to be identified because he was not authorized to speak to the media.
The authorities are investigating the explosion, he said.
A fire official said the series of explosions may have come from large quantities of sulfur, ammonia and sulfur trioxide, which becomes sulfurous acid when mixed with water, stored at the compound.
Win Tun, who lives near the warehouses, said she heard a "very big, loud noise of explosion," which prompted startled residents to try to flee.
"Some people ran in the wrong way. I didn't know where to run to," she said, adding that the initial blast was followed by a string of other explosions.
The dead include four firefighters, MR TV reported.
The strength of the explosion shattered the windows of nearby houses. Source