MANILA (2nd UPDATE) – The explosion that rocked a unit in Two Serendra on May 31 was not caused by a bomb, Department of the Interior and Local Government Secretary (DILG) Manuel "Mar" Roxas II said Friday.
In a press conference on Friday, Roxas said all signs point to gas explosion, likely from liquefied petroleum gas (LPG), as the cause of the blast which damaged Unit 501B of Two Serendra in Bonifacio Global City in Taguig.
Roxas said all nine K-9 units from different handlers did not find any bomb residue during the course of the investigation.
"Talagang sinuyod ito ng mga aso at wala silang nakitang residue or presence of explosive materials," he said.
Likewise, the result of walk throughs by various investigators from the Philippine National Police (PNP), National Bureau of Investigation (NBI) and Bureau of Fire Protection (BFP) found no traces of a bomb.
Roxas explained that the PNP, which conducted the first walkthrough after the exhaustive surveys of the K-9 units, did not find any bomb component at the blast site.
"Iyung buong grounds nilakad nila, may arms-length distance para walang mamintis na bagay. Tinitignan ang dinadaaan nila at tsaka yung grounds mismo at wala silang nakita na bomb component gaya ng shrapnel, blasting caps o timers na commonly nakikita kung bomba ang pagsabog," he said.
A swab test conducted by the Scene of the Crime Operatives (SOCO) from all the concrete slabs that were thrown off the unit were negative for any bomb residue.
Roxas said the swabs were tested using Gas Chromatography Mass Spectrophotometer which can detect RDX, PETN, TNT, TATP and other organic explosives.
A post-blast investigation conducted by the NBI, meanwhile, checked the debris and rubble found at the scene. The NBI said no crater or seat of explosion was found, bolstering the conclusion that a bomb was not the cause of the blast.
The BFP also conducted an investigation and found out that "despite the presence of ?re, charring and singeing, neither bomb components nor a crater was found or detected."
Three people died in the blast after a concrete slab fell on a nearby delivery van.
LPG caused the blast
Roxas said the findings point to a gas explosion, with liquefied petroleum gas (LPG) as the possible culprit.
The Two Serendra condominium uses a centralized piped-in LPG system.
However, Roxas said that at this point, what triggered the gas explosion has yet to be established, with the condominium occupant Angelito San Juan still unable to speak, and a deeper investigation still ongoing.
"Hindi natin masasagot iyan hanggang matapos yung imbestigasyon natin na more science than police work," Roxas said.
Dr. Carlos Primo David of the National Institute of Geological Sciences of University of the Philippines Diliman said the blast was consistent with a gas explosion.
David said that an analysis of the blast revealed that the explosion was most likely caused by combustion or reaction of chemical substances (gases).
He said the following explosion characteristics were observed at the Serendra blast site:
1. Minimal post explosion residue
2. No blast cratering
3. Instantaneously dissipated ?ame
4. Minimal charring
5. Powerful and widespread pressure wave
6. Almost instantaneous explosion covering a large area
Earlier, it was also reported that renovations were made inside the unit. However, Roxas said it has not been established whether the renovation contributed to the blast.
Parties acted 'normal'
Dismissing the terrorism angle, Roxas said the tenants and owners of the condominium unit "acted normal" prior to the explosion.
Angelito San Juan is a US green card holder with no criminal record. He arrived in Manila on the day of the explosion and is still in the intensive care unit (ICU) of St. Luke's Medical Center in Taguig.
He was in Manila to attend a wedding and asked Mariane Cayton-Castillo, through Herminia Ochoa, that he be allowed to use the condominium unit during his stay in the country.
Ochoa is a friend of San Juan and the aunt of Cayton-Castillo, who is now based in the US. She is the designated caretaker of the unit.
Roxas said San Juan, who was earlier tagged as a "person of interest" in the case, is still unable to speak.
San Juan sustained second-degree burns in 72% of his body, according to his doctors.
Investigators gathered 53 sworn statements from at least 60 interviews with people who may help determine the cause of the explosion.
No finger-pointing yet
Roxas said now is not yet the time to determine who should be held liable for the blast.
"Wala pa. Tinatapos natin ang report. Kung sino man ang dapat na managot, will go through a different process, para masiguro na unang-una, hindi ito bomba, wala tayong pangamba na nagkakaroon ng urban terroristic attack," he said.
"Ngayon nakikita natin na gas ito, kaya pumipihit na ngayon sa preventive measures at pagsisiguro na di maulit ito."
Roxas said investigators are now working with the Bonifacio Gas Corporation, the supplier of piped gas for establishments at Bonifacio Global City.