Photo taken on June 3, 2013 shows the accident site after a fire occurred at the Jilin Baoyuanfeng Poultry Company in Mishazi Township of Dehui City, northeast China's Jilin Province. (Xinhua/Wang Haofei)

CHANGCHUN -- At least 55 people were killed on Monday morning in a poultry processing plant fire in northeast China's Jilin Province, rescue headquarters confirmed.

The fire broke out at around 6:06 a.m. at a slaughterhouse owned by the Jilin Baoyuanfeng Poultry Company in Mishazi Township of Dehui City, according to firefighters.

Over 300 workers were in the plant when the accident happened, survivors told Xinhua, adding they heard a sudden bang and then witnessed dark smoke at around 6 a.m.

About one hundred workers have managed to escape from the plant whose gate was locked when the fire occurred, said survivors.

The complicated interior structure of the prefabricated house in which the fire broke out and the narrow exits have added difficulties to the rescue work, sources with rescue forces said.

As of 12 a.m. on Monday, the fire has not been put out and rescue work is ongoing.

The exact number of those trapped in the plant has not yet been confirmed and further investigation into the cause in under way.