Media playback is unsupported on your device Media caption Survivors told state TV how they escaped from the blaze

A fire at a poultry processing plant in China has killed at least 119 people, officials say.

The fire broke out at a slaughterhouse in Dehui in Jilin province early on Monday.

Accounts speak of explosions prior to the fire, which caused panic and a crush of workers trying to escape. Most exits were said to be locked.

A labour activist told the BBC it was the worst factory fire in living memory.

The fire is now said to have been mostly put out and bodies are being recovered.

President Xi Jinping, who is on a visit to the Americas, ordered every effort to go into the rescue operation and treatment of survivors, adding that the investigation into the cause of the accident would be vigorous.

Sources including the provincial fire department suggest there may have been an ammonia leak which either caused the fire or made fighting the blaze more hazardous.

Media playback is unsupported on your device Media caption Footage from inside the plant shows burning embers and piles of ash, as Damian Grammaticas reports.

Other reports speak of an electrical fault.

It is China's deadliest fire since 2000, when 309 people died in a blaze in a dance hall in Luoyang, in Henan province.

About 100 workers had managed to escape from the Baoyuan plant, Xinhua said, adding that the "complicated interior structure" of the building and narrow exits had made rescue work more difficult.

It said the plant's front gate was locked when the blaze began, and other official media reports said there was only one unlocked door in the whole building.

Firefighters have still not completed the job of recovering bodies from the building, meaning the death toll may rise yet further, say correspondents.

Some 60 injured people have been sent to hospital, but the severity of their injuries remains unclear. State media quoted hospital staff as saying that some wounded were being treated for inhalation of toxic gases such as ammonia while others had burns of varying degrees.

Pictures from the scene showed the roof mostly burned away to reveal blackened, twisted girders.

The provincial government said it sent more than 500 firefighters and at least 270 doctors and nurses to the scene, evacuating an area nearby that is home to 3,000 people as a precaution, reported Reuters news agency.

Analysis China's central government in Beijing has created thousands of workplace safety regulations, from the handling of toxic chemicals to the prevention of occupational illnesses. But those laws are not always enforced, since local officials and factory bosses often place profits ahead of safety. Many buildings in China, including factories, are constructed without consideration for health and safety concerns. Worries over factory thefts often dictate that building exits are locked, making it difficult for workers to leave in a hurry. The authorities in Beijing are attempting to change that pattern. Workplace accidents have dropped by a third in the past five years, according to comments attributed to former Vice-Premier Zhang Dejiang. The death toll from those accidents dropped by almost the same proportion. However, China's Public Security Bureau notes that in 2011 fires on construction sites rose nearly 6% and in agricultural factories nearly 9% compared to 2010. Factory bosses failed to obey safety procedures, using heat sources and electricity in unsafe ways, it said. Critics argue that factory bosses are rarely punished for workplace accidents. Poultry plant fire raises safety concerns

Panic

Workers interviewed by state broadcaster CCTV said the fire broke out at about 06:00 (22:00 Sunday GMT) during a shift change and may have started in a locker room.

Those who managed to escape from the factory describe panic and chaos as the lights went out, the building filled with smoke, and they found exits blocked or locked.

Guo Yan told Xinhua the emergency exit for her workstation was blocked and that she was knocked to the ground in a crush of workers trying to escape through a side door.

"I could only crawl desperately forward," said Ms Guo, 39. "I worked alongside an old lady and a young girl, but I don't know if they survived or not."

Another unnamed survivor said: "I escaped by climbing out of a window. There was a huge cloud of black smoke coming down the corridor. It was burning hot. It engulfed me. As soon as I was outside I collapsed unconscious."

Family members were quoted as saying the factory doors were always kept locked during working hours.

The plant is owned by Jilin Baoyuanfeng Poultry Co. It was only established in 2009 and is not an antiquated facility.

Located around 800km (500 miles) north-east of Beijing, it employs some 1,200 people and produces some 67,000 tonnes of chicken products every year.

Chickens are slaughtered at the plant and then cut up for retail - a process that takes place in cold conditions. Ammonia is used as part of the cooling system and in such plants flammable foam insulation is commonly used to keep temperatures low.

Workplace safety standards are often poor in China, with fatal accidents regularly reported at large factories and mines, says the BBC's John Sudworth in Shanghai.

Those lax standards are variously linked to corruption, the prioritisation of efficient production over worker safety in building design, and poor enforcement of safety rules.

Comments posted on the Chinese micro-blogging site Weibo about the fire included: