An explosion at a state-owned coal mine in northeast China killed at least 51 miners Sunday night, delivering another blow to the Chinese government just hours after it restored running water to the nearby city of Harbin following a massive toxic chemical spill.

State media said 70 miners had been rescued by noon Monday at the Dongfeng Coal Mine in Qitaihe, located 200 miles east of Harbin in Heilongjiang province. But with another 100 still trapped, the 9:40 p.m. explosion could be among the deadliest this year in China, where as many as 10,000 die in mining accidents each year despite the government's repeated vows to enforce safety regulations.

Zhang Zuoji, the provincial governor, arrived at the scene of the mine explosion just hours after he was shown on state television visiting a home in Harbin and taking the city's first drink of tap water after a five-day shutoff.

The explosion drew attention again to the Chinese government's poor industrial safety record just as the ruling Communist Party was trying to put the crisis in Harbin behind it and portray itself as committed to preventing such disasters.

The water supply in Harbin, a city of 3.8 million people, came back on at 6 p.m., state-run news media reported. Earlier in the day, the city announced that levels of toxic substances in the Songhua River had fallen within safety standards as a 50-mile slick of benzene and other poisonous chemicals moved downstream.

It will take time to flush out sediment from the pipes, state media said, and city workers were still treating the water with disinfectants.

The city said the public should expect interruptions in water service in the days ahead, as well as televised color-coded bulletins about water quality -- red when unusable, yellow when suitable for washing and cleaning, green when safe for drinking.

"So far, the water is as normal as it used to be: colorless, transparent and no special smell," said Wang Yanli, 23, a waitress at a dumpling restaurant. "We're already using it for cleaning."

But even as life began returning to normal in the city, the toxic pollution moved through rural villages and towns downstream. It is expected to flow through the port city of Jiamusi before entering the Heilong River, crossing into Russia and contaminating the water supplies of the city of Khabarovsk at week's end.

The Chinese government says that rural residents along the Songhua have been warned of the pollution and that most rely on underground sources of water that are not linked to the river. Jiamusi, a city of about 800,000, also relies on well water, state media said.

But Russian authorities in Khabarovsk were airlifting in 20 tons of active carbon to strengthen the municipal purification system and preparing plans to shut down the water supply in the city of 700,000, news agencies said.

On Saturday, the Chinese government made a rare public apology to Russia for any harm resulting from the benzene spill, which was caused by an explosion Nov. 13 at a state-owned petrochemical plant in nearby Jilin province. Officials at first denied the blast led to any pollution, but admitted the disaster last week.

Benzene can cause some forms of cancer, anemia and other blood disorders, as well as kidney and liver damage. No cases of poisoning have been reported by the government, but experts have warned of long-term damage to the ecosystem that could increase the risk of cancer for residents in the region for years.

The city has temporarily banned fishing and the sale of fish or other food from the river.

China's secretive leaders have yet to offer an explanation or punish any officials for trying to hide the chemical spill from the public. Instead, they have restricted reporting and ordered state media to focus on the government's efforts to ensure clean water for the city.

Those efforts have highlighted the Communist Party's organizational strength. Thousands of party members, government workers and soldiers were mobilized to dig wells, install a huge filtering system and truck in and distribute clean water to residents across the city. The success of the complex operation helped calm public outrage over efforts to conceal the spill.

Still, interviews over the past few days suggest that the attempt at a coverup has shaken the public's already fragile confidence in the party. Several residents expressed skepticism about the government's promise to punish those responsible for the spill, and others said they would be wary of its claims about the safety of the water supply.

"I definitely won't be using the water right away," Wan Qingzhi, 61, a retired fertilizer company official, said after an afternoon jog on Stalin Avenue, the promenade that runs alongside the Songhua River in downtown Harbin. "I'm going to wait and see what happens first."

As China's economy booms, environmental damage has been a persistent byproduct. A recent government report said that up to 70 percent of China's rivers and lakes are dangerously polluted, and the air in several cities is some of the most polluted in the world.

Party officials have often sought to defend the government's environmental record by arguing that China is too poor and unemployment too high to put the environment ahead of economic growth. But many residents rejected that argument.

"What good is economic development without water? Or without your health?" said Shi Huipin, 23, a phone company employee.

Frustration with the party's failure to enforce anti-pollution regulations has emerged as a major political challenge for the party and has sometimes triggered protests and riots. In Harbin, many residents accused party officials of trying to hide the spill because they were more concerned about protecting their careers -- and kickbacks they receive from polluting factories -- than about the health of ordinary citizens.

"The damage to the environment is linked to corruption and the pursuit of profits," said Zheng Shengli, 53, a laid-off welder.

Hu Fengbin, 49, a lawyer, blamed the pollution on a string of factories upstream on the Songhua River, but especially the huge Jilin Petrochemical facility where the spill occurred. The company is a subsidiary of one of the government's biggest oil firms, China National Petroleum Corp., and many believe its political influence allows it to ignore environmental regulations.

After the spill, Hu filed suit against the company. Almost immediately, he began receiving phone calls from others who wanted to join the lawsuit.

Hu said it was unclear whether the party-controlled courts would allow the case to go forward. Officials have already ordered reporters not to write about it, he said. "But it doesn't matter whether we win or lose," he said. "We're putting more pressure on them to clean the river."

Workers at a water processing plant in Harbin take part in a test run to resume service. The city was without water service for five days.