The whir of choppers and the buzz of chain saws were all that was heard on Monday near the mining town of Itogon as workers looking for bodies dug through the mud using shovels and their bare hands — the ground too wet for heavy machinery.

Francis Tolentino, a senior adviser to President Rodrigo Duterte, estimated that nationwide 5.7 million people had been affected by the storm, which hit the country at the height of its powers, with wind speeds topping 150 miles per hour.

The authorities said the prospectors, some of whom are believed to be children, were working illegally at the mine site, which was shut down in the 1990s amid concerns of environmental degradation.

After Benguet Corp., the company that previously operated the mine, halted operations, thousands of individuals flocked to the site, known as Antamok, to work the tunnels started by the company.

“Before Ompong came, I asked them to leave,” Victorio Palangdan, the mayor of Itogon, said of the miners, using Typhoon Mangkhut’s local name. He said the workers at the camp told him that they had permission from Benguet Corp. to work the abandoned mine, a claim the company denied.

By some estimates, as many as 400,000 small-scale miners operate throughout the Philippines, digging in areas where such activity is outlawed and using banned toxic substances, including mercury, to process their finds.

Mr. Duterte inspected part of the disaster area on Sunday, and met with top officials in Tuguegarao City for a televised briefing on the damage and the recovery effort.

“I share the grief of those who lost their loved ones,” the president said.

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