MANILA - The head of the Philippine National Police (PNP) on Sunday offered possible explanations on why the man who confessed to butchering a family in Bulacan has tested negative for drug use despite an earlier admission that he was high on shabu during the murders.

The drug test for construction worker Carmelino Ibañez, 26, may have turned out negative because he took a low-grade variant or a small quantity of shabu, said PNP chief Director General Ronald "Bato" dela Rosa.

"Posible na iyung drugs na ini-take niya is mahina ang quality o mababa ang quantity," Dela Rosa told radio DZMM.

The suspect, he added, also took the drug test more than 48 hours after the murders. A urinalysis can only detect drugs in the body up to 48 hours after it was taken.

Ibañez earlier admitted that he was drunk and on drugs when he killed Estrella Carlos, her mother Aurora Dizon and Carlos’s three children aged 1, 7 and 11 last June 27.

The 26-year-old suspect also told reporters that he raped both Estrella and Aurora. He later denied this in an extrajudicial confession.

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Dela Rosa said Ibañez's earlier admission of the crime would have greater effect on the rape and murder charges against him, compared to the negative drug tests.

"Mas mabigat iyung sinabi niya talaga, iyung galing sa kanyang bibig na hindi siya under duress, inamin talaga niya," he said.

The country's top cop vowed to search for more evidence against the suspect and his alleged accomplices, aliases "Tony" and "Inggo," who both remain at large.

"Assurance ko sa inyo talaga, ginagawa namin ang lahat para mabigyan ng justice ang pamilya," he said.

Dela Rosa said President Rodrigo Duterte is also emotionally invested in the case.

"Nagfa-follow-up siya 'pag mga sensational crime... Hindi iyan nakakatulog dahil nanggigil siya," he said.

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