A powerful explosion suspected to have been caused by a faulty appliance ripped through a residential building in an upscale district of the Philippine capital on Friday night, killing three people in a passing delivery van that was hit by debris, authorities said.

The explosion punched a large hole in the wall of the apartment building and sent concrete chunks flying onto the street below. Three people in the van were crushed to death and four other people were injured, property owner Ayala Land Inc. said in a statement.

A telephone operator at the Taguig city police station, who declined to give her name because she was not authorized to speak to the media, said the explosion came from an appliance and was not caused by a bomb.

Interior Secretary Mar Roxas, who visited the site with President Benigno Aquino III, told reporters that the building was evacuated and all possible angles were being investigated. He said a forensic examination was not yet finished.

"This could be an accident, this could be an explosion of chemicals. This could be anything. Let us not speculate," he said. He urged the public to refrain from speculating if the blast was linked to recent travel advisories issued by the U.S., British, Canadian and Australian governments for the restive southern Philippines, where they cited a risk of kidnappings and terrorist activities.

Muslim militants have targeted the Philippine capital in the past, but most attacks have been confined to the southern region, where minority Muslims have fought for self-rule for decades.

Two apartment units in the building were totally "blown out," said George Marco, spokesman for Ayala Land.

The area was cordoned off and police, fire and rescue teams put up a makeshift medical center to treat casualties, said Joel Montales, an administrator of Taguig city, where Serendra is located.