MANILA -- A supermarket in Pampanga province should not have been flattened by a powerful quake earlier this week had the Building Code been followed, the Philippine Institute of Volcanology and Seismology said Thursday, as rescuers halted a search for survivors.

Authorities on Wednesday stopped rescue efforts, saying "proof of life" has faded from underneath the rubble of the Chuzon Supermarket in the agricultural town of Pampanga, from where 5 fatalities were pulled out.

The "very strong" Intensity 6 ground shaking generated by Monday afternoon's Magnitude 6.1 quake should have only caused minor damage to infrastructure, said Phivolcs Executive Director Renato Solidum.

"Sa Intensity 6, hindi kami nag-i-expect ng significant na damage sa isang building. Kung sumunod sa Building Code, 'di iyan dapat mag-collapse. Mabitak lang, minor damage lang ang inaasahan," he told radio DZMM.

(With Intensity 6, we do not expect significant damage on a building. If it followed the Building Code, it should not have collapsed. Only cracks, minor damage are expected.)

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Surrounding structures were left intact after the quake, but the supermarket's beams and pillars split, he noted.

"Hindi naman angkop iyung mga materyales na ginamit. Hindi talaga sila ready for earthquake," said Solidum.

(The materials used were not appropriate. They were not ready for the earthquake.)

President Rodrigo Duterte earlier said business operations of all branches of Chuzon Supermarket should be suspended after its Porac branch collapsed during Monday's quake.

• Duterte wants Pampanga grocery chain to suspend operations after quake

The Building Code specifies the appropriate size and spacing of beams, posts and steel rods so that a structure can withstand up to Intensity 8 shaking, said Philippine Institute of Civil Engineers (PICE) Director Frederick Sison.

PICE and Phivolcs developed a questionnaire with which the public can determine whether or not their houses are quake-resistant, he added.

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When Monday's quake struck at rush hour last Monday, office workers in Metro Manila evacuated skyscrapers, train services were halted and penthouse swimming pools burst.

Less than 24 hours later, a Magnitude 6.5 temblor rocked parts of Visayas, and Bicol and Caraga regions on Tuesday afternoon. Authorities said the 2 earthquakes were unrelated.