A 43-year-old man under the supervision of the Fauquier County Sheriff's Department died Tuesday at Fauquier Hospital, where he had been taken four days earlier from the county jail.

Sheriff's Capt. Fred Pfeiff said an internal investigation is underway to determine what caused the death of Herman N. Jenkins Jr., of Bealeton, who was arrested Oct. 29 for violating the conditions of his probation.

Pfeiff would not disclose the preliminary results of an autopsy performed Wednesday in Fairfax or provide details about Jenkins's incarceration.

Members of Jenkins's family said in an interview that they think he was suffering from heroin withdrawal and was denied proper medical attention. "There are a lot of unanswered questions," said Pat Washington, 40, one of Jenkins's sisters and health coordinator for the Head Start program run by the Fauquier Community Action Committee Inc.

Sheriff Joe Higgs Jr. declined to comment on the allegation. He said the investigation was not prompted by any suspicion of wrongdoing and is routine under the circumstances. He said that the jail has certified medical staffers on call 24 hours a day and that there are policies regarding inmates suffering from drug withdrawal.

According to Peggy Gates, an official with the Virginia Office of Probation and Parole, Jenkins was on probation after being convicted in D.C. Superior Court on a charge of heroin possession. She said she could not disclose the specific probation violation of which he was accused.

Washington said Jenkins, a bricklayer who is survived by four grown children, his parents, four sisters and two brothers, learned that he was to be charged with a probation violation and drove himself to his probation officer's office Oct. 29. She said he expected to wait in a local jail cell to be taken to a drug treatment facility near Richmond.

"He drove himself there," she said. "He was in good health."

But Washington said he told her in a phone conversation shortly after his arrival at the jail that he was experiencing symptoms of heroin withdrawal and was not receiving treatment. By the end of the first week, Washington said, Jenkins had stopped calling. But on Nov. 6, a Saturday, she said another inmate's mother called the Jenkins family after visiting the jail.

The woman said her son had told her "that Herman was vomiting and delirious and had a high fever," Washington said. She said her mother called the jail immediately and was told to call back Monday; when her mother called back, Washington said, she was told that Jenkins was okay.

Washington said the next time she spoke to her brother was Nov. 12 in the hospital, where doctors told her he had a collapsed lung. Washington said the family was notified of Jenkins's condition several hours after he was admitted.

Authorities said Jenkins was taken to the hospital in a police cruiser that day. Peter Fakoury, a hospital spokesman, said Jenkins originally was treated for pneumonia and was admitted to the intensive care unit. Health experts say pneumonia is common among drug users, whose immune systems are likely to be compromised.

Washington said her brother was in and out of consciousness until the next day, when he stopped breathing for several minutes and was revived. She said doctors told her afterward that he probably had lost most of his brain function.

Pfeiff said an internal investigation has begun "to determine the circumstances and nature of the death."

Washington said sheriff's investigators told her not to believe rumors of mistreatment being spread by inmates at the jail. "The only thing I know is that the sheriff's investigators told us that inmates lie," she said. "Do I believe that inmates are lying now? I don't know."