MANILA, Philippiens -- Due to the type of firearms used and the brazenness of the attack, the Manila Police District said on Monday that only one group could be behind the gruesome robberies in Paco, Manila, and Cabuyao, Laguna.

Chief Inspector Dominador Arevalo Jr., head of the MPD homicide section, said he requested the Scene of the Crime Operatives (Soco) division for a cross-matching of the spent shells of .45 guns found in the two robberies that occurred four days apart.

The cross-matching, he said, would determine if the shells were fired from the same gun.

On May 12, robbers killed lawyer-businessman Alfred Dy, who had just withdrawn P1 million from Banco de Oro, and responding Manila cops Francisco Neri and Jose Santos in Paco.

Armed men stormed a bank in Cabuyao and shot dead nine people, mostly employees of the Rizal Commercial and Banking Corporation. The 10th victim died on Sunday in a hospital.

Arevalo said they were still hunting down two members of the notorious "Forex gang" who were tagged by three witnesses in the Manila robbery.

Former Philippine Army corporal Juanito Boton and Edmund Mendoza alias Gilbert Collado were identified through pictures provided by police. They were previously arrested for a string of robbery cases that victimized foreign-exchange shops in the city.

Boton was reportedly one of three men involved in the shootout with Neri and Santos.

"We knew it from the first day of investigation but we did not divulge it to the media because we wanted them caught. We are still pursuing follow-up operations for their arrest," said Arevalo.

The homicide chief explained that the suspects may have switched from preying on forex shops to banks since they were already identified with forex robberies.

Meanwhile, the National Bureau of Investigation (NBI) will assist the Philippine National Police in the probe of the massacre at the RCBC Cabuyao branch massacre last Friday.

NBI director Nestor Mantaring ordered deputy director for regional operations services Reynaldo Esmeralda to deploy the agency's district offices in Laguna, Batangas, Lucena and Cavite to aid the Task Force RCBC.

Esmeralda said they dismissed the testimonies of two minors who allegedly witnessed the robbery-massacre due to "conflicting statements."

"They're probably just after the reward," he said of the P2-million bounty for those who could provide information on the robbers.