The weekend gas explosion, China's worst mining accident in two years, was a blow to the government's efforts to improve safety standards in an industry that is the deadliest in the world.

Grieving relatives, who wailed at the gate of the Xinxing mining office yesterday, were shocked that such a blast could occur at one of China's state-run mines, which the government has promoted as being safer than smaller, privately run concerns.

But even as officials hustled to calm the families, miners idled near the shafts in their battered work clothes, waiting for word that their shifts might start again. "Economic necessity," one said.

China's hunger for energy is cutting closest to the bone in places such as Hegang, an aging industrial city near the Russian border where the economy runs on coal. The country uses coal to meet three-fourths of its electricity needs.

Officials have said 528 miners were underground when the Xinxing mine exploded after a gas leak. Besides the 104 confirmed dead, four people are missing and feared dead, the Xinhua news agency said.

The head of China's State Administration of Work Safety told Xinhua that the mine's management failed to evacuate workers promptly. His deputy went further, saying the mine had too many platforms and workers inside, in an effort to increase output.

Deputy chief Zhao Tiechui called the structure "far too complicated for its current ventilation system to work effectively." He did not specify what the mine's capacity was.

China has closed hundreds of smaller, private mines or absorbed them into state-owned operations, which are considered generally safer. But some of the deadliest accidents this year continue to be at state-run mines.