Multiple murder and multiple frustrated murder cases were filed on Wednesday against nine people implicated in the explosion in Davao City on September 2 where 15 people died.

The Special Investigation Task Group (SITG) lodged the complaint before the Office of the City Prosecutor past 5 pm, Senior Superintendent Valeriano de Leon, the head of the task group, said in a text message to Daily Manila Shimbun.

A suspect, who is the alleged bomber, has been identified. But De Leon and other police officials declined to divulge his identity except he is aged 20 to 30 years old.

Mentioning his name in public would only give him the chance to evade arrest if a warrant is issued, de Leon said.

"I am expecting all of us will cooperate for the meantime...It would be better for law enforcement officers if there is a warrant of arrest," De Leon said in a news briefing aired over radio two hours

"We will reveal his name at a proper time. It will be evaluated by the prosecutor," said De Leon.

Philippine National Police Director General Ronald Dela Rosa revealed in an earlier interview the suspected bomber is hiding in an area protected by a lawless group in central Mindanao.

The others are composed of five men and three women, who are still unidentified.

De Leon said the bomber was identified through accounts of survivors and witnesses.

"He was the one seen who brought and left the explosive placed in a bag," the official said.

One of the witnesses is a taxicab driver where the alleged bomber and some companions boarded. "The driver overhead their conversation," De Leon said without elaborating.

On the alleged involvement of Vice Mayor Abdul Wahab Sabal, Senior Superintendent Michael John Dubria, Davao City police chief said it is still being investigated.

"It's still under investigation. As of the moment, we are focused on the primary suspect," said Dubria in an interview over ANC.

The 15th fatality is a pregnant woman who died Monday evening. Vicenta Asperin, 21, and massage therapist passed away at 10:17 pm. Asperin, six months pregnant, had been in a coma for 11 days at the Metro Medical and Research Center, said a statement from the Davao City government.

"According to the medical report of the City Social Services and Development Office, Asperin died of heart failure and brain damage," the statement read.

Authorities did not include her unborn baby in the count of fatalities as based on the notes from the Local Civil Registrar. Emmanuel Tupas.