A large pre-dawn explosion at a warehouse in Burma’s biggest city Rangoon on Thursday killed at least 17 people and injured dozens but was not caused by a bomb, an official said.

“It was not a bomb explosion,” the official said, though the cause of the blast, which sparked a large fire that destroyed many nearby storage places and homes, was still unknown.

At least 17 people, including four firefighters, had died, while 79 people were injured, including around 30 firemen, another government official told AFP.

Residents in several areas of the city were woken by the blast around 2:00 am local time (1930 GMT), which appeared to have hit a medical warehouse in the eastern township of Mingalar Taung Nyunt, witnesses told AFP.

Firefighters battled for hours to douse the flames and finally succeeded in extinguishing the massive fire at around 6:45am, leaving behind a scene of utter devastation.

The second government official said the blast had created a large crater and damaged several warehouses and around 50 houses in the area, most of them wooden dwellings.

An AFP photographer at the scene saw rescue workers frantically searching for survivors and pulling a dead body from the debris.

In a city not unused to bomb blasts, the sound of the unexplained explosion overnight brought hundreds of worried locals into the streets after they were abruptly woken from their sleep.

“We heard a very loud noise from the explosion and saw smoke in the sky. Our building was also shaken by the explosion. We have no idea what’s happening,” a resident in nearby Botahtaung township told AFP.

A rescue centre has been set up at a nearby monastery to provide shelter to around 100 people made homeless by the fire, the AFP photographer said.

The first funerals will be held as early as Thursday afternoon, he added.

Last week, a blast caused by an explosive device killed one woman and wounded another in northern Rangoon.

While the cause of Thursday’s incident remains unclear, Burma has been hit by several bomb blasts in recent years, most of them minor, which the authorities have blamed on armed exile groups or ethnic minority fighters.