MANILA, Philippines -- The Senate will consult its own explosives experts on the cause of last year’s explosion at the Glorietta 2 mall in Makati City that killed 11 people and wounded more than a hundred others, Senator Gregorio Honasan said Thursday.

Honasan, who chairs the Senate committee on public order and illegal drugs, also said at least two more technical working group meetings to consolidate the conflicting findings of the Philippine National Police (PNP) and experts contracted by mall owner Ayala Land Inc.(ALI).

After the ocular inspection of the blast site by Honasan’s committee Thursday morning, the PNP and ALI both stood pat their clashing findings. The PNP has concluded the explosion was caused by a buildup of gasses in the mall’s basement while ALI’s experts insist it was a bomb.

Honasan said the Senate would seek experts, possibly from the University of the Philippines, to help it.

The senator, a former soldier, refused to make his own conclusions after the ocular inspection, although he noted that the “columnar effect” of the explosion is similar to that caused by a grenade blast.

“We should be careful about making statements in a highly political situation...that would reveal unnecessary biases,” Honasan said, adding the objective of the Senate investigation into the incident is to amend, repeal, or upgrade the Fire Code, Building Code, the Human Security Act (Anti-Terror Act), and rules on disaster preparedness.

Chief Superintendent Luizo Ticman, of the PNP-Southern Police District, insisted that all evidence -- scientific, physical, forensic, and documentary -- point to a methane-gas explosion followed by a diesel-vapor-gas blast.

But biogas expert from the United Kingdom Dr. Stephen Etheridge maintained that biogas accumulation could not have caused the explosion, and forensics expert from Malaysia Aini Ling said traces of the explosive RDX were found at the explosion site.

“I find it very difficult to understand how such an amount of biogas could cause such a problem” when the sump pit in the Glorietta 2 basement opens to the atmosphere and there is regular transfer of waste, Etheridge said in a press conference following the inspection.

Asked if their findings could be taken to be self-serving, Etheridge and Ling said they would not change the facts for anybody.

Ling found RDX in five swabs and one scraping in the basement during her own inspection on November 2 and 6, or more than two weeks after the October 19 incident.

But Ticman said the crime labs of the National Bureau of Investigation and the PNP, the United States' Federal Bureau of Investigation, Australian Federal Police, and the Philippine Institute on Pure and Applied Chemistry “took swabs everywhere and all turned up negative.”

“There is no need to re-investigate1...There is no need to change our conclusion that the conditions prior to the explosion allowed the accumulation and production of biogas that later on exploded,” Ticman said.

Superintendent Fennimore Jaudian, of the Department of Interior and Local Government's Inter-agency Anti-arson Task Force, said the starting point of the blast -- the mall basement -- was well-guarded and even had a closed-circuit television to record everyone coming in and out of the area.

“If it were really a bombing, [ALI] should have presented the CCTV monitoring system to us,” Jaudian said.

Ticman also said if RDX had really caused the explosion, traces of the explosive would be found everywhere, not in selected areas.

In the Senate hearing prior to the inspection, the authorities admitted that RDX does not occur naturally and is also a restricted substance.