GUIYANG, Feb. 19 (Xinhua) -- Three people were killed and four others injured, including three who were seriously injured, in a coal mine blast in southwest China's Guizhou Province, local authorities said Tuesday.

The blast occurred around 5:25 p.m. at the Kaifa coal mine in Jinsha County, when officers from a local police station and coal mine workers were destroying expired explosives, sources with the county government said.

The three who sustained serious injuries have been sent to a local hospital.

An investigation into the cause of the blast is underway.