Six people are dead and two are ill with carbon monoxide poisoning after a build-up of the gas in a dormitory in China's capital on Monday, local police said on Wednesday.

The deaths occurred at 6:40?AM when eight migrant workers aged 20 to 50, from Hebei and Shandong provinces and Inner Mongolia Autonomous Region, were sleeping in their dormitory at a trade firm in Daxing District, in the southern suburbs of Beijing.

Police sources said six workers died at the scene and two were sent to hospitals for emergency treatment, where they were described on Wednesday as out of danger and stable.

The preliminary investigation showed the carbon monoxide build-up was mainly caused by the "low air pressure", which led to an incomplete burning of the coal used for cooking and heating, and prevented the poisonous gas from escaping through the chimney.

Further investigations on the case are underway.

In many areas of north China, burning coal in stoves remains the main method of cooking and winter heating for rural residents and urban dwellers living in old buildings.

(Xinhua News Agency March 14, 2007)