Rescuers worked in frigid cold to reach miners trapped half a kilometer underground as the death toll from a huge gas explosion Nov. 21 jumped to 104.

The pre-dawn blast at the state-run Xinxing mine in Heilongjiang province near the border with Russia was the latest to hit China's mining industry — the world's deadliest. Authorities say safety is improving, but hundreds die in major accidents each year.

A total of 528 people were working in the 100-year-old mine at the time of the 2:30 a.m. explosion, the State Administration of Work Safety said.