XI'AN -- Rescue work has been suspended due to toxic gas in a coal mine where four workers are trapped underground in Northwest China's Shaanxi province, local authorities said Saturday.

All rescuers had been evacuated from the coal mine as of 1:30 pm, and the situation of the four trapped workers is still unclear, according to authorities.

A fire happened at about 11:30 am Friday in the shaft of a colliery run by Xinhe Coal Mining Company in Chengcheng County, when 10 workers were doing some repair work underground, the county government's information office said in a statement. Six workers escaped, leaving four trapped in the mine.

Experts are currently working to create a new rescue plan.