BEIJING/CHENGDU  -- Approximately 50 miners were trapped underground after a gas blast occurred in a coal mine on Wednesday afternoon in the southwestern province of Sichuan, said the nation's work safety authorities.

The gas explosion took place at the Xiaojiawan Coal Mine in Panzhihua, according to the State Administration of Work Safety (SAWS).

The SAWS said it has sent a work team to the mine to oversee the rescue work.

An initial investigation found that 120 miners were working underground when the blast occurred at around 6 pm, sources with the rescue headquarters said.

As of 9:30 pm, 70 people had been lifted out of the mine and 50 others remained trapped underground, according to the sources.

The coal mine is owned by Zhengjin Industry and Trade Co, Ltd in Panzhihua, some 750 km southwest of the provincial capital Chengdu.