MANILA — Authorities are looking into more possible mass graves at the New Bilibid Prison following the discovery of "human bones" in the state penitentiary, Justice Secretary Jesus Crispin "Boying" Remulla said Friday.

The bones, identified by the National Bureau of Investigation as human remains, were found in a septic tank at the penitentiary's "Sputnik" area, Remulla told ANC's "Headstart."

He said the human remains were discovered while authorities were searching for inmate Michael Angelo Cataroja, who was reported missing since July 15.

However, authorities have yet to ascertain if the remains were that of the missing inmate, Remulla said.

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During the search efforts, the justice secretary said "a lot of oral history came out about the mass graves" inside Bilibid's 10-hectare maximum security prison.

Inmates who have stayed in Bilibid "for a long time" claimed some people who disappeared ended up in "septic tanks or in one more mass graves," which Remulla said they have yet to locate.

"But the two septic tanks have been pointed out as possible areas where human remains have been put in the past and we are looking into it," he added.

Remulla said they were seeking the help of experts from the archeology and forensic departments of the University of the Philippines to investigate the matter and "look at the timelines."

This week, Bilibid was placed under red alert status after a fight inside the maximum security compound left one inmate dead and 9 more injured.

• Bilibid under red alert after prison fight leaves 1 dead
• 1,000 Bilibid personnel sacked after prison fight leaves inmate dead

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