China’s top leader, Xi Jinping, called on Saturday for a redoubled rescue mission in northern China after a gas explosion in a mine there killed more than 80 people and left others trapped underground, the Chinese state news agency said.

Mr. Xi “stressed the need to make every effort to treat the injured, organize search and rescue operations scientifically and properly handle the aftermath,” the agency, Xinhua, reported. He also called for an investigation into the explosion, which happened on Friday night, and emphasized the need to “hold those responsible to account, according to the law.”

Mr. Xi’s decision to quickly, and personally, issue a statement may indicate that Chinese officials expected the situation to worsen. The death count rose drastically on Saturday, reaching at least 82 after an initial report of eight.

When the explosion occurred on Friday night, at the Liushenyu coal mine in Shanxi Province, 247 workers were underground. As of Saturday morning, the cause of the explosion was still unknown, according to CCTV, the Chinese state broadcaster.

Li You contributed research.