SAN DIEGO (FOX 5/KUSI) -- A 46-year-old man died Saturday while in sheriff's custody, officials with the San Diego County Sheriff's Department confirmed. Around 9 a.m., sheriff's homicide investigators were notified of his passing. At this time, the man's name has not being released. The department said they are working to locate and notify his family. Prior to his passing, the man told deputies on Dec. 24 that he was having flu-like symptoms. The department said he was seen by medical staff who then ordered testing. As a precaution, he was placed in medical isolation to prevent potential spread. Later on Dec. 28, deputies noticed the man sitting on the floor of his cell while conducting their weekly hygiene inspection around 8 a.m. According to the department, the individual was breathing but did not respond to the deputies. About 10 minutes later, two Medication Assistance Treatment deputies and a nurse came to his cell. The nurse checked his vitals and offered him medication. While the nurse was talking to the man, he started having difficulty breathing and went into medical distress. At that point, staff provided emergency medical aid to the individual until relieved by Vista Fire Department personnel. Despite their efforts, the man passed away at the detention center. The individual was taken into custody on Nov. 25, 2024, on a felony warrant for bringing controlled substances into a jail or prison, the department confirmed. At the time of his arrest, he was believed to reside in Escondido. The Sheriff’s Homicide Unit responded and are conducting an investigation, per protocol for all in-custody deaths. The cause and manner of his death will be determined by the San Diego County Medical Examiner’s Office.