The death toll has risen to 19 from a fire at a coal company's office building in China's northern Shanxi province, Chinese state media said on Thursday.

The fire broke out at 6:50 a.m. at the four-story Yongju Coal Industry Joint Building in China's top coal-producing hub of Shanxi. State broadcaster China Central Television initially reported the fire killed 11 and injured at least 51.

The cause of the fire was still under investigation.

Calls to Yongju Coal Industry were not answered.

China's coal producers are under scrutiny for a series of accidents in mines in recent months, which has weighed on production as mines stop work for safety inspections. (Reporting by Colleen Howe; Editing by Miral Fahmy and Muralikumar Anantharaman)