YANGON (AFP) - A pre-dawn blast at a warehouse in Myanmar's biggest city killed at least 17 people and injured dozens more on Thursday, sparking a blaze that took firefighters hours to tame, officials said.

Officials ruled out a bomb but said they had yet to determine the cause of the explosion in Yangon, formerly the capital.

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

"It was not a bomb explosion," a government official told AFP.

The flames engulfed several buildings in the warehouse compound and destroyed around 50 homes in the area, most of them wooden dwellings.

At least 17 people, including five firefighters, had died, while 81 others were injured, 37 of them firemen, said Thein Htun Oo, deputy director of Yangon's fire services department.

Firefighters battled through the night to douse the flames and finally succeeded in extinguishing the massive fire at around 6:45 am, revealing a scene of utter devastation.

An AFP photographer saw rescue workers frantically searching for survivors, carrying young children to safety and pulling a dead body from the burnt-out rubble, while dazed locals surveyed the shells of blackened buildings.

The blaze left hundreds homeless, another government official said.

"Around 900 people are homeless now and they are sheltering at nearby monasteries serving as rescue centers," he said.

"About seven warehouses were totally destroyed. The responsible officials are still trying to find out what happened," he told AFP. One resident, Khin Hla Kyi, said she feared for her life as she fled the encroaching fire, which devoured her home and all of her possessions.

"We had to run for our lives," she told AFP. "Now we have nowhere to go. My house was destroyed." The blast also created a huge crater at least 10 metres (33 feet) wide and several metres deep, filled with ash, plastic and metal debris.

Dozens of rescue workers and onlookers crowded around the gaping hole to take stock of the damage on Thursday, when white smoke could still be seen billowing from the site.

"There will be a funeral for our five firemen this evening. We will honour them.