MANILA – The owner of a grocery in Porac, Pampanga which collapsed during a strong quake Monday has been placed under police custody, authorities said.

Samuel Chu, owner of the ill-fated Chuzon Supermarket in Porac town, and assistant manager Kaye Toledo, have been placed under police custody so they could answer some questions regarding the collapsed structure, according to Senior Superintendent Christopher Abrahano, chief of Philippine National Police – Criminal Investigation and Detection Group in Central Luzon.

Abrahano said investigators are now identifying the contractor and engineer of the structure.

"Una, sole proprietorship ba ito o korporasyon? Pangalawa, sino ang mga contractors ang ginamit niya…aalamin namin sa kanya ang circumstances ng pag-komisyon niya ng paggawa ng building," Abrahano said.

(First, we have to know whether this is a sole proprietorship or a corporation. Second, who were the contractors? We have to know the circumstances behind the construction of this building.)

Abrahano said they will also investigate the safety and regulation officer responsible for ensuring that the building met safety standards.

"Kasama sa iimbestigahan ang regulation officer, saan at kanino dumaan ang mga papeles," Abrahano said.

(We will also investigate the regulation officer, who handled the papers.)

Porac Mayor Condralito Dela Cruz earlier said the structure was relatively new, built only 4 years ago.

At least 4 bodies have been retrieved from the supermarket's Porac branch which collapsed, while 8 people have been pulled out alive from the rubble as of 5 a.m. Tuesday, the Pampanga Disaster Risk Reduction and Management Office (PDRRMO) said.

Rescue efforts are underway at the collapsed supermarket, as there are still signs of life under the rubble, according to Senior Supt. Samuel Tadeo of the Bureau of Fire Protection.

The PDRRMO said it has also ordered the temporary closure of Chuzon Supermarket branches in Apalit, Sto. Tomas and Guagua towns to give way to structural assessments.

• ‘There are still signs of life’: Search continues at collapsed Pampanga supermarket
• 'Lord, have mercy': Quake survivor recalls time in smashed Pampanga mart

At least 16 people were killed in the earthquake, one of the strongest to strike close to the densely populated Philippine capital in years.