Science minister and veteran seismologist, Renato Solidum, said many students survived because they were attending the morning assembly, which happens every Monday.
“They were lucky to be outside. They were able to stay put and sit down,” Solidum told DZMM in a separate interview.
“These areas have experienced strong earthquakes before. This is one of the strongest.”
One viral video showed a branch of beloved fast-food chain Jollibee in General Santos City collapsing as onlookers watched in horror.
The chain issued a statement on Monday night saying all its staff in earthquake-hit areas are safe.
President Ferdinand Marcos Jr said he had mobilised the entire government machinery to respond to the calamity.
His transportation and health secretaries have flown to Mindanao from the capital Manila to oversee the response. Health secretary Teodoro Herbosa said aftershocks, some of them quite strong, hit even as doctors treated the injured.
Access to some towns, such as Jose Abad Santos in Davao Occidental on Mindanao’s east side, remains difficult.
Mayor Jason John Joyce told DZMM that landslides have buried his town’s only highway, leaving half of it accessible by road.
“Relief goods have to be flown in to far-flung barangays (villages),” he added.