The International Criminal Court (ICC) could issue additional arrest warrants for individuals identified as co-perpetrators in former President Rodrigo Duterte's controversial war on drugs, according to the lawyer representing the victims' families.

Atty. Joel Butuyan, speaking in a television interview, pointed out that Duterte’s ICC warrant refers to him as an "indirect co-perpetrator", suggesting others may also face legal action.

"If you read the arrest warrant, there are indications that there are others besides President Duterte. Because the description given to President Duterte was indirect co-perpetrator," Butuyan said.

He added that Senator Ronald "Bato" dela Rosa, who served as Philippine National Police (PNP) chief during Duterte’s presidency, may be among those who could face an arrest warrant in the coming days.

Former Senator Antonio Trillanes IV, who previously filed cases against Duterte at the ICC, echoed this view.

"We are still expecting an arrest warrant, but it may only be for Bato dela Rosa," Trillanes said.

As PNP chief from 2016 to 2018, Dela Rosa was instrumental in carrying out Duterte's anti-drug campaign, which resulted in thousands of killings, many of which were extrajudicial.

Butuyan also revealed that more Filipino witnesses are expected to testify at the ICC regarding the alleged crimes against humanity linked to Duterte’s drug war.

A victims’ counsel will also be formed to represent the families of those killed during the campaign.

Authorities served Duterte’s arrest warrant from the ICC on Tuesday morning. Later that evening, a chartered flight carrying Duterte left the Philippines for The Hague, Netherlands.

His plane made a layover in Dubai early Wednesday before continuing to Rotterdam The Hague Airport at around 5:15 a.m. (Dubai time).

The ICC investigation continues as the international court seeks accountability for crimes against humanity linked to Duterte's drug war.