Workers get prepared for rescue work in Dongning, Heilongjiang province, Jan 30, 2013. [Photo by Zhang Chunxiang/Asianewsphoto]

HARBIN - Death toll rose to 12 Wednesday afternoon from a coal mine accident in Northeast China's Heilongjiang province, local authorities said.

Three workers have been pulled to safety. The three were lifted out of the mine at around 11 a.m. Wednesday and were in stable condition, according to the Dongning County government.

Three workers entered the Yongsheng colliery to pump out water, but poisonous gas caused them to faint around 10:30 a.m. Tuesday.

Rescuers were sent to the site, but some of them were also affected by the toxic gas.

Rescue work is still underway.

Rescuers said the poisonous gas may have been carbon monoxide.

The private, licensed mine has an annual capacity of 50,000 tonnes.

A worker injured in a coal mine accident is loaded into an ambulance in Dongning, Heilongjiang province, Jan 30, 2013. [Photo by Zhang Chunxiang/Asianewsphoto]