LANZHOU - The death toll in a carbon monoxide poisoning incident which occurred in a lead-zinc mine in Northwest China's Gansu province has risen to five as two more bodies were recovered Thursday afternoon, local authorities said.

Three people remain missing, the provincial administration of work safety said in a statement.

Three inspectors were doing routine inspections in an underground pit at the Changba Lead-Zinc Mine in Chengxian county of the city of Longnan at 9 am Wednesday.

After the inspectors failed to return by that afternoon, mine managers sent 11 workers to look for the missing inspectors. Of the 14 people that entered the mine, five returned unharmed and one was rescued later. The single rescued worker is in critical condition.

A rescue team has installed ventilation equipment to facilitate searches for the three workers who remain missing.

The mine belongs to Baiyin Nonferrous Metals Group Co, Ltd, a major Chinese producer of non-ferrous metals.