An explosion occured at a fireworks factory in northeast China's Heilongjiang Province Monday.

Thick smoke blankets the scene.

There are usually 40 to 50 people at work in the factory on workdays. The exact number of workers who were in the factory when the explosion occurred is unknown.

More than 550 fire fighters and soldiers in 20 fire trucks were dispatched to the scene.

Some 300 rescuers are on their way to the scene to search for survivors.

"Fire trucks are hosing water onto nearby storehouses to prevent another explosion," said Xu Zhaojun, Party chief of Yinchun City.

More than 2,000 residents were evacuated after the initial explosion.

No other information was immediately available.