MANILA, Philippines — Up to eight inmates fought at the Philippine national penitentiary Wednesday, leaving a high-profile Chinese drug lord dead and four other inmates injured, officials said. The melee occurred amid a congressional investigation into the drug trade within the facility.

Justice Secretary Vitaliano Aguirre II said a riot broke out Wednesday after an inmate reprimanded three Chinese drug convicts who were using methamphetamine.

He identified the dead as Tony Co. He said Co and two other injured Chinese convicts are among the biggest drug traders in the country. Also injured was Jaybee Sebastian, a prison leader being asked by officials to testify in the congressional investigation against Senator Leila de Lima.

De Lima, a former justice secretary, has said Sebastian was a tipster who gave her department information that led to a 2014 raid of the penitentiary. The raid exposed how high-profile convicts lived in air-conditioned villas equipped with hot tubs and disco lights. Guns, counting machines, cellphones and other gadgets were confiscated.

As former head of the Commission on Human Rights, De Lima earned Duterte’s ire for investigating his alleged links to death squads in southern Davao City, where was mayor. She also recently led a Senate investigation into Duterte’s anti-drug war that has left more than 3,000 suspected drug pushers and users dead.

Duterte has accused De Lima of collecting money from the illegal drugs trade operated by drug lords from the penitentiary — a charge de Lima calls “lies.”

Bureau of Corrections director Rolando Asuncion says the seven to eight inmates involved in the riot are from two rival gangs. The violence ended quickly and occurred in a contained area separate from the larger inmate population. He said it’s not clear what kind of injuries the victims sustained but an ice pick and other materials were confiscated.

De Lima expressed doubts Wednesday that what happened was a real riot, saying the prisoners involved were those who refused to testify against her.