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MANILA - Commission on Human Rights (CHR) chairperson Chito Gascon said Tuesday that their investigation into the thousands of killings carried out by the government's drug war remains a struggle.

He said the police continues to withhold records on the anti-drug operations.

"Tinanong na namin sa pulis na puwede ba ibigay niyo sa amin lahat ng records niyo sa lahat ng mga napatay. Eh hanggang ngayon pinagkakait pa rin sa amin," Gascon told "Bandila sa DZMM."

CHR is currently investigating 1,500 cases in the drug war. The death toll, Gascon said, could be as high as 27,000.

"Maliit kumpara sa laki ng bilang ng nangyari dahil hindi sapat ang impormasyon na umaabot sa amin," he said.

• Duterte drug war: A timeline

Data from the Philippine National Police as of Aug. 2018 showed that nearly 5,000 deaths were recorded in police anti-drug operations since the Duterte administration launched its campaign in July 2016.

The police also recorded some 23,000 homicide cases under investigation (HCUIs) or killings still under probe.

As the country observes National Human Rights Consciousness Week from Dec. 4 to 10, Gascon said it is important to remind the public about the importance of human rights.

"Ang bawat tao ay may karapatan at ang estado ay may tungkulin na pangalagaan 'yan," he said.

In the case of war on drugs, right to due process and presumption of innocence should be upheld, Gascon reiterated.

"Last week, may Kian Delos Santos case. Sinabi ng mga pulis na nanlaban si Kian, eh hindi pala. Ilan pa kaya ang mga ganiyan?" he said.

• 3 cops found guilty of murder over Kian Delos Santos slay

Three Caloocan cops were sentenced to reclusion perpetua or 20 to 40 years in prison after they were found guilty of murder for the teenager's slay.

Delos Santos' death prompted government action against alleged irregularities in the drug war.

The leadership of the campaign was transferred from police to the Philippine Drug Enforcement Agency (PDEA). The case also sparked a Senate inquiry.