Some human rights advocates believe Mr. Kandahari is being held in the National Directorate of Security’s Unit 124, which they have denounced as a prison where torture is routine. Unit 124, across the street from the American and NATO military headquarters in Kabul, is one of the Afghan detention sites on a proscribed list by the American military, which is not allowed to transfer prisoners to facilities where torture is believed to be used. However, that ban does not apply to the Central Intelligence Agency, which often has personnel in Unit 124, activists say.

Mr. Kandahari is wanted in connection with the disappearances and deaths of many of 17 Afghan civilians who were detained by an American Special Forces A Team for which he worked. Afghan investigators said they uncovered a videotape showing Mr. Kandahari torturing one civilian, Sayid Mohammad, who was later found dead, and said there was substantial evidence to prove that American personnel had been involved in the detentions of the missing civilians.

The bodies of 10 victims were found near the Special Forces base beginning in April, after the Americans left; the last was discovered on June 4, according to Afghan forensic investigators and relatives of the victims. They had disappeared between November and February.

The American military did not respond to requests for comment on Sunday, but in May, an American official insisted that the A Team was not to blame for the disappearances and deaths. “We have done three investigations down there, and all absolve I.S.A.F. forces and Special Forces of all wrongdoing,” the official said, referring to the NATO-led International Security Assistance Force. “It is simply not true.”

A representative for Human Rights Watch in Afghanistan, Heather Barr, said: “The U.S. said they investigated thoroughly, there’s nothing there, so everyone should go away and accept their word that they checked and did nothing wrong? I don’t think that ends the discussion. There’s a lot more explaining that needs to be done that hasn’t happened yet.”