MANILA - A Senate committee resumed on Thursday its investigation on the wave of killings linked to President Rodrigo Duterte's war on drugs, under its new head, Senator Richard Gordon.

Gordon replaced Sen. Leila De Lima, who was ousted by her fellow lawmakers after she presented a self-confessed hitman who claimed Duterte ran a vigilante hit squad in Davao City during his term as mayor.

"Iwawasto lang po natin nang walang duda [We will make things right to erase doubts]," Gordon said in his opening statement. The President's allied had criticized De Lima's handling of the hearing as biased.

Some senators accused De Lima of coaching witness Edgar Matobato, who said he was a member of Duterte's hit squad.

De Lima is being accused by the Duterte and several witnesses of receiving millions in drug payoffs during her term as justice secretary.

During Thursday's hearing, senators again questioned Matobato's credibility after De Lima said he just volunteered to appear before the Senate.

"There is a security issue here. The witness just appeared here, he testified here, nobody invited him," said Sen. Panfilo Lacson.

De Lima explained that she was contacted by Matobato's representative last August 29 and was told that the former DDS hitman wanted to meet with her.

"[The person] told me that 'remember the self-confessed DDS hitman that was taken in by the DOJ under the Witness Protection Program when you were still secretary of justice? [He said] he wants me to tell you that he now desires to [testify]'," she said.

She then met with him last October 2 in a safehouse and confirmed his desire to surface.

When Senator Alan Peter Cayetano asked why the justice department wasn't able to file any case while they still had Matobato in custody, De Lima said she had formed a special team to look into his claims but that there was no update yet when she left the department.