A fire at a complex of iron mines in northern China killed at least 33 miners and trapped another 28, state media reported Monday.

Rescuers had pulled 45 miners to safety by late Sunday, the state-run newspaper China Daily cited local officials as saying.

The blaze erupted Saturday morning after an electric cable caught fire at the mines in Shahe in Hebei province (search), the official Xinhua News Agency reported. The fire spread quickly to five connected mines, it said.

The China Daily cited Zhang Fumin, a Shahe government official, as saying 33 bodies were recovered. State media reports said 106 miners were working underground when the fire started.

Thick smoke hindered rescue efforts, and emergency workers sought help from experts from the provincial government, the Beijing Youth Daily newspaper reported.

Police have detained the bosses of the mines and frozen their bank accounts, it said.

Premier Wen Jiabao called for the miners to be saved "at any cost," it added.

China's mines are the world's most dangerous, with thousands of deaths reported every year due to fires, cave-ins and other disasters often blamed on indifference to safety rules or lack of required equipment.

The government has repeatedly vowed to do more to stop the disasters.

Coal mines account for most of the fatalities, but accidents that claim dozens of lives at a time also are regularly reported in iron, tin and other mines.