Story highlights More than 300 workers were inside at the time

Escapees tell Xinhua the gates were locked when the fire breaks out

Authorities do not know how many people are trapped in the plant

The "complicated structure" and "narrow exits" are posing difficulties for rescuers

An early morning fire at a poultry processing plant in northeast China killed at least 119 people Monday, state-run Xinhua news agency said.

Another 54 workers were injured.

More than 300 workers were inside the plant in Jilin province when the fire broke out about 6 a.m., Xinhua said.

About 100 of them were able to escape -- and told Xinhua that the gates to the plant were locked.

"Suddenly, the lights inside went out and the plant got quite dark," a worker named Wang Fengya told the news agency.

Photos: Deadly fire at Chinese poultry plant Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – Smoke billows from a large poultry processing plant in Mishazi Township of Dehui City in northeast China's Jilin Province on Monday, June 3. More than 300 workers were inside the plant when the fire broke out about 6 a.m., the state-run Xinhua news agency said. More than 100 people were reported killed in the fire. Hide Caption 1 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – Family members of missing workers wait for information. Hide Caption 2 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – People gather at the site of the fire, which an official says was started by an explosion. Hide Caption 3 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – Two women wait for news about a family member. It took six hours to bring the fire under control. Hide Caption 4 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – An injured worker is wheeled into a hospital in Changchun. Hide Caption 5 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – A nurse provides medical treatment to an injured worker who escaped the poultry plant. Hide Caption 6 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – The interior of the poultry slaughterhouse is left in ruins. Hide Caption 7 of 8 Photos: Deadly fire at Chinese poultry plant Deadly fire at Chinese poultry plant – Firefighters work at the accident site. A Xinhua news agency report says the plant's complicated interior structure and narrow exits have made the rescue work difficult. Hide Caption 8 of 8

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"When I finally ran out and looked back at the plant, I saw high flames."

Firefighters battled the blaze for six hours before they were able to bring it under control.

A fire official told CNN that an explosion at the plant started the fire -- but the cause of the blast wasn't immediately known.

"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," the Xinhua report said.