HEGANG, China — The coal mine that exploded in northern China, killing 104, had too many workers underground in an effort to increase output, a government official said today, exposing the risks often taken to meet the country's insatiable energy demands.

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

Grieving relatives, who wailed at the gate of the Xinxing mining office this morning, were shocked that the 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.

China's hunger for energy cuts closest to the bone in places like 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. Most escaped, but 104 were confirmed dead and an additional four were missing and feared dead, the official Xinhua News Agency reported today.