Rescue work is underway. ?

The death toll has climbed to 11 in Tuesday's factory explosion in north China's Hebei Province, the emergency rescue headquarters said Thursday.

The accident happened at around 11 p.m. Tuesday in the four-story dormitory building of a privately-owned plant that produces slabstone in Niugang Village of Yixian County.

Ten people were killed at the scene and another one died at hospital.

One worker suffered slight injuries and was still in hospital Thursday.

Investigators said the accident was caused by illegally possessed explosives.

Local police said they had detained three suspects in connection with the explosion, but refused to give details.