MANILA, Philippines??Who is responsible? At this point all we can say is speculation,? President Benigno Aquino III said Tuesday night as he also disclosed that all intelligence agencies were in the process of identifying those behind the EDSA bombing that killed four, two instantly, and injured 14 others.

The bomb placed under the seat in the middle of a passenger bus driven by a man ironically named Maximo Peligro went off just before 2 p.m. on Epifanio de los Santos Avenue (EDSA) near the north gate of the upscale Forbes Park subdivision in Makati City.
The blast blew a huge hole on the right side of the northbound Newman Goldliner plying the Baclaran-SM Fairview route.

Makati Mayor Junjun Binay said the explosion was so powerful that it punched a hole in a nearby concrete fence.

?It appears that it was a big bomb that exploded but we?re still determining what kind of bomb,? said the Makati police chief, Senior Supt. Froilan Bonifacio.

The explosion shattered the windows of the air-conditioned bus (Plate No. TXJ-710), which was approaching the loading bay on EDSA and Metro Rail Transit station on Gil Puyat (formerly Buendia) Avenue.

Police said the sixth row on the right side of the bus sustained massive damage.

The attack came two months after the United States and several other Western governments warned that a terrorist attack in Manila was imminent, and followed a bus hijacking in August last year that left eight Hong Kong tourists dead.

The President said terrorists were behind the explosion that ripped through the bus.

At a news briefing, Mr. Aquino said he received intelligence reports last year that ?a Muslim secessionist group? was planning a ?bombing? attack but did not have the resources to mount it.

Wondering how the group was able to mount the attack, the President ordered a probe of the bombing.

?Everybody can be assured that in the soonest possible time, like many other incidents such as the bar exam bombing, there will be a solution to this situation,? he said.

Mr. Aquino expressed his sympathies to the families of those who died and who were wounded in the blast.

When he arrived at the site 10 minutes after the explosion, Binay said he saw blood and severed body parts on the bus.

He said he also saw a severely injured man through the big hole.

Two of the victims were killed on the spot. The two others died in the hospital, police said.

Both legs of a female fatality, who was yet to be identified, were cut off from the thighs, according to a survivor.

?She must be at least 18 years old,? said Susanna Flores, among the seven passengers brought to Ospital ng Makati.

She said the other fatality, Johansson De Leon Reyes, of Plaridel, Bulacan, was covered in blood and ?his left leg was at a funny angle as if it had been broken off.?

A woman whose identity is yet to be established, sustained a head wound. ?I was told she jumped off the bus. She was the first to be wheeled into the hospital,? Flores said.

Mary Grace Buen Borondia, 29, of Maybunga, Pasig City, was first brought to Ospital ng Makati but was later transferred to Makati Medical Center.

Other casualties brought to Ospital ng Makati were identified as Anabel Gozon, 40, of Barangay Sampaloc, Tanay, Rizal; Antonio Lino, 41, of San Mateo, Rizal; Jeffrey Victoriano, 27, of Taguig City; and Irish Teniola, 22.

Ten of the victims were taken to St. Luke?s Medical Center at Bonifacio Global City in Taguig. They were Roy Saguit Rivera, 40; Fe An Padilla Sy, 25; Fleur An Padilla Sy, 48; Aiza Hutalle Peralta, 26; Virgilio Aquino Reyes, 76; Paul Richard Obial Reyes, 41; Jennifer Valdez Andoque, 19; Veronica Sanchez Gando, 24; and Gloria Aquino Reyes, 71.

An investigation report issued by the Makati police Tuesday night said the fatalities were Johansson De Leon Reyes, who died on the spot; Mariano Magayaw Salustiano, 57; Shirley Khristel Hausena Andes, a female wearing a silver necklace marked ?Krish? and an unidentified man brought to St. Luke?s who died while being treated.

The report was signed by Chief Insp. Genaro Peruda, staff duty officer.

A doctor said those who survived the blast sustained minor injuries, mostly in the feet.

?Basically these are minor injuries. We haven?t seen anyone with a fracture,? said Dr. Joven Cuanang, chief medical officer at St. Luke?s Medical Center.

Maximo Peligro and Michael Haralde, the driver and conductor of the bus, respectively, were taken into police custody for investigation.

At a Makati police station, Peligro said he smelled gunpowder right after the blast. ?If it was a normal explosion, there would be no smell of gunpowder,? he told reporters.

He discounted mechanical failure as the cause of the explosion, saying that the bus was well-maintained.

Peligro, who was unharmed, said that the bus windshield was not damaged by the explosion. He said he kicked it to enable him and the other passengers to get off the vehicle.

He said two men, who acted strangely, quickly got off the bus just moments before the explosion. ?They were moving from one seat to another although we had no idea there was an explosive aboard,? Peligro said.

Haralde said the two men hopped on the bus in Baclaran, Parañaque City, took seats in the middle section and got off on Evangelista Street in Makati.

Haralde, who sustained injuries on both legs, said the bus had 20 passengers when it left Baclaran. It became almost full when it stopped at a loading bay on Evangelista.

He said almost half the passengers disembarked at EDSA Ayala.

The driver and the conductor said the explosion happened before the bus reached EDSA corner Buendia.

Authorities are considering an improvised explosive device as the cause of the blast.

?We have yet to gather all the debris and reconstruct the fragments to categorically determine what type of explosive material was used,? said Director Nicanor Bartolome of the National Capital Region Police Office.

Bartolome said the footage taken by the closed-circuit television (CCTV) camera of the Metropolitan Manila Development Authority (MMDA) would be a big help.

MMDA Chair Francis Tolentino said the agency had turned over copies of footage from its CCTV cameras to investigators hoping to find out the identities of the suspects.

For more than four hours, the road from Ayala to Buendia was closed off to traffic to allow police to examine the scene, resulting in heavy buildup of vehicles along the northbound at grade section of the Skyway and along EDSA from Roxas Boulevard.

The bus was moved to the Southern Police District (SPD) in Taguig City at 7:45 p.m. where investigators will conduct further technical investigation of the vehicle.

Mr. Aquino inspected the bus half an hour later for about 15 minutes. He was joined by Bartolome and Chief Supt. Jose de los Santos of the SPD.

He visited the victims at St. Luke?s Medical Center Tuesday night. With a report from Agence France-Presse