A third round of testing at the Pasteur Institute in Phnom Penh has confirmed that about 90 people from Roka commune in Bat­tambang province are, in fact, infected with HIV, a day after Prime Minis­ter Hun Sen said he did not believe the outbreak was actually AIDS.

Preliminary testing for the virus at the Roka commune health center in Sangke district, which began on December 8, showed that about 110 residents out of about 800 tested were infected with HIV, including 19 children.

Of the 90 villagers who had tested positive at the center as of Tuesday, 89 again showed a positive result in a second test at the provincial referral hospital on Wednesday, before their blood samples were sent to the Pasteur Institute for a third round of testing.

Contacted by telephone Friday, Dr. Didier Fontenille, the director of the Pasteur Institute, said staff at the French medical nonprofit worked late into the night Thursday analyzing the samples.

“Unfortunately, I have to confirm that all of the blood samples provided by the Ministry of Health are positive. They have HIV,” Dr. Fon­tenille said.

“Yesterday we received around 90 samples and confirmed all these samples, but probably to­day or tomorrow we will re­ceive some more samples and will do the testing for the information,” he added.

The third round of positive results came after Mr. Hun Sen said he was all but certain that the spate of positive HIV results—which has caused panic among villagers and sparked a major investigation by local officials and international health organizations—was due to faulty testing equipment.

“So far, I 99 percent do not believe that it’s AIDS,” Mr. Hun Sen told about 1,000 graduates during a speech in Phnom Penh on Thursday.

“If out of 800 people, 106 are infected, that’s the end of us,” he said. “Probably, if we were tested using those machines, half of us would be infected by AIDS. I still don’t believe it. I don’t believe it.”

Asked to provide an update on the situation Friday, both Voeung Bunreth, director of the Battam­bang provincial health department, and By Beng Sor, chief of the Roka commune health center, declined to comment.

Mean Chhi Vun, director of the Health Ministry’s National Center for HIV/AIDS, Dermatology and STD (NCHADS), said he also did not have any update on the number of infections, as his team had spent Friday collecting information from villagers in an effort to determine the source of the virus.

“I did not go to the health center, I just [went] to the village for mapping,” he said, adding that NCHADS workers had assured concerned villagers that care would be available to those who need it.

An investigation into the outbreak has so far centered on Yem Chrin, an unlicensed doctor who regularly treated villagers in the commune with injections and intravenous drips.

During a search of his home Thursday, police collected at least 20 needle tips as they inspected the remnants of a recent trash fire behind the building, while dozens of empty vials littered the area around the house.

Battambang provincial deputy police chief Chet Vanny said that Mr. Chrin, who was detained for questioning by police on Wednesday, remained in their custody as of Friday afternoon—partly for his own safety as authorities fear a backlash from angry villagers.

James McCabe, director of operations for the Child Protec­tion Unit, a police unit that is supported by the Cambodian Children’s Fund and is aiding the investigation, said it would be premature to put the blame on any one person.

“It’s not going to be a quick, overnight investigation,” Mr. Mc­Cabe added. “It needs to be, and it will be, a thorough inquiry into who, what, when and why, and that is essential…so that this never happens again.”

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