The death toll of the most powerful earthquake to hit the Philippines in decades rose on Tuesday to 38 people, with nearly 500 others injured, 20,000 displaced and many others still believed trapped in damaged buildings as rescuers searched for them.

Randy Bacag, 23, said his mother, Amie Bagan Bacag, 42, was doing the laundry when the 7.8 earthquake shook the southern Philippines on Monday morning. She rushed out of her home at the foot of a mountain near the shore of their village on Balut Islands. Then, she remembered her granddaughter who was playing next door, Mr. Bacag said in an interview.

As Ms. Bacag turned back, rocks came crashing down the mountainside, he said, burying the houses beneath them. She was trapped under the rubble with her 6-year-old granddaughter, Tresia Dalaman, Tresia’s 6-year-old cousin Brian John Mangayao, and the children’s 62-year-old great-grandmother, Pilar Singcag.

More than 24 hours later, their bodies had yet to be recovered.

Mr. Bacag believes all four are dead, but the family cannot not hold a wake, bury their loved ones or even begin mourning.

“I just hope we can still recover the corpses even if it’s only their bodies,” Mr. Bacag said.

His father, who was also running to safety, watched the disaster unfold and now seems like a different person, he said. “It’s like something snapped in him.”

The quake, which struck in the morning on the first day of classes, caused severe damage in General Santos, a city of 700,000 people known for its tuna industry. It damaged bridges, roads, government offices, markets, shops and other buildings, including five schools, according to a local official, Romdel Catolico.

Thousands of people fled to 44 evacuation centers and some spent the night outdoors. Harold Cabreros, administrator of the Office of Civil Defense, said some are still afraid to stay indoors because of the frequent aftershocks.

Allan Angcad, 66, is clinging to hope that his daughter, Babylyn Angcad, 28, a manager of a Savemore supermarket in General Santos, is still alive.

Ms. Angcad had only been assigned to her post for a week and was one of two people reported missing from the store, he said.

“Her siblings rushed here,” Mr. Angcad said. “We were all trying to contact her, but there was no response.”

Rescuers told him “there were signs of life,” he said in a phone interview.

In the villages of Balut Islands, to the south of General Santos, recovery efforts have been slow. Vivian Bulabos, a local official, said the seaport was damaged, and because the area can only be reached by boat, some of the injured had to be airlifted to the mainland.

“We need a backhoe to recover the bodies, but the equipment is not available,” she said.

Communications were also disrupted. Home to about 700 families, the area now has only one working internet connection.