What caused the Serendra blast and its aftermath?

Interior Secretary Mar Roxas says authorities are focusing on gathering evidence from the Two Serendra condominium unit in Global City, Taguig, where a deadly blast occurred on May 31.
Investigation is centered on Unit 501B – the “blast site” – as authorities finished scouring through the street portion of the “crime scene.” Roxas says authorities want to interview occupants of the condominium to help establish a “narrative timeline” of events. Investigators are particularly interested in the unit’s occupant Angelito San Juan, who is now in intensive care at St. Luke’s Medical Center. Police has not determined the cause of the explosion. Roxas says 3 teams of bomb-sniffing dogs initially found no residue of bombs or explosive devices in the area. The explosion that occurred shortly past 8 pm on Friday knocked out the wall of the Serendra unit, sending a huge chunk of rubble that pinned down a delivery truck. Three were killed — Marlon Castillo Bandiola, 29; Jeffrey Cunanan Umali, 32, from Sta Mesa, Manila; and Sallymar Natividad, 41, from Bulacan.

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