The death toll more than doubled overnight, the official Xinhua News Agency reported. A duty officer at Xinxing's work safety authority and an employee at the company that owns the mine confirmed 87 had died.
Ventilation and power were restored in the mine, said the employee, who refused to give his name because he was not authorized to speak to the media. The mine's director, deputy director and chief engineer were fired Saturday, he said.
A total of 528 people were working in the Xinxing (pronounced shin-shing) mine at the time of the 2:30 a.m. explosion Saturday, the State Administration of Work Safety said in a statement. Xinhua reported 420 escaped.
Steam was seen Sunday rising from the site of the explosion, which resulted from a gas build-up. The blast littered the ground with shards of shattered glass and twisted pieces of metal. A building next to the mine lay crumbled, its blackened roof on the ground.
The site was cordoned off by police tape and guarded by a half-dozen officers while a handful of passers-by watched as rescue teams entered the mine shaft.
Tang Cunha, a local resident who stood about 30 yards (meters) behind the police tape, likened the destruction caused by the blast to that of a massive earthquake. "I had to come by and see it," he said. "It's awful, it's awful."
Survivors recounted their harrowing escapes. Wang Jiguo, 35, a miner who monitored gas levels in the shaft, said he suddenly grabbed two other workers near him and started scrambling to the door, shouting: "Run quickly, don't carry anything!"
At the entrance of the shaft, Wang and Fu Maofeng, 48, phoned other workers who were still underground and told them to escape, Fu told Xinhua from the intensive care unit of a hospital in Hegang, where he was being treated.
"Just after we hung up the phone, we heard a loud bang from inside the shaft. The entrance of the shaft started shaking," Fu said. Then a wave of searing hot air slammed them to the ground, knocking them unconscious.
When he came to, Fu found himself lying in the hospital, his face covered with scratches and burns on his left eye. "Our team has 10 people, and I don't know how they are now," Fu said.
Company officials remained hopeful of finding survivors.
"If we haven't found them, to us that means they are still alive," San Jingguang, a spokesman for the mining company, told reporters. "Rescuing people is still our first priority."
State-run CCTV displayed a diagram showing the miners trapped about a third of a mile (half a kilometer) underground. One entrance was blocked, and rescue teams in orange work suits and yellow hard hats were sent underground in mining carts down a separate shaft.
Overnight temperatures dropped as low as 14 degrees Fahrenheit (minus 10 degrees Celsius), according to the Central Meteorological Station.
Xinxing, which started operations in 1917, is located near the border with Russia. Large state-owned coal mines, such as Xinxing, are generally considered safer than smaller, private ones that account for the bulk of production. Saturday's blast underscores the difficulties the government faces in trying to boost safety while maintaining output.
Heilongjiang provincial governor Li Zhanshu urged officials to better manage coal mines. "Development is important, but the growth of GDP shouldn't be achieved at the price of miners' blood," he told Xinhua.
Coal is vital to the vast population and booming economy, as China uses it to generate about three-quarters of its electricity.
The government has cracked down on unregulated mining operations, which account for almost 80 percent of the country's 16,000 mines. It says the closure of about 1,000 dangerous small mines last year has helped it cut fatalities.
Yet major accidents persist. In the first nine months of this year, China's coal mines had 11 such incidents with 303 deaths. Gas explosions were the leading cause, the government said.
A blast at the Tunlan coal mine in northern China's Shanxi province in February killed 78 people. In December 2007, a gas explosion at another Shanxi coal mine killed 105 people.