XI'AN - Five people were killed and two rescued after a fire broke out at a gold mine pit in northwest China's Shaanxi province Thursday evening, local authorities said Friday.

The accident occurred at about 6:30 pm Thursday as welding sparks ignited the fire on wooden scaffoldings at the mine run by Xinglong Mining Co. in Tongguan county that was undergoing a safety overhaul, the county government said.

All six trapped underground by heavy smoke have been pulled to the ground by Friday morning, but four died as medical treatment failed and the rest two are in normal condition, it said in a news update.

In addition, one rescuer was killed by carbon monoxide poisoning during the rescue operation.

An investigation into the cause of the fire is under way.