Efforts are under way to rescue the remaining miners at the Xiaojiawan mine in Panzhihua city in Sichuan province.
The blast happened on Wednesday evening when about 150 miners were underground, city officials said.
By Thursday morning, more than 100 people had been rescued and taken to hospital, reports said.
Chinese state television said rescue teams had retrieved the bodies of 16 miners who died from carbon monoxide poisoning. Another three people died in hospital.
The mine is owned by Zhengjin Industry and Trade Co Ltd. Its officials are assisting in a police investigation, the city government said in a statement on its official microblogging site.
Accidents are frequent in China's mining industry, which is criticised for poor safety standards.
Official figures show that 1,973 people died in coal mining accidents in the country last year.
While this represented a 19% drop compared to the year before, some have suggested that actual numbers could be higher as not all incidents may have been reported.
China's central government has introduced measures aimed at improving standards but these directives are often ignored at local level.
A gas explosion at a coal mine in south-west China has killed 19 people and left 28 trapped underground, state media say.