March 23, 2026 – Riverside County Sheriff’s Office officials report that in June 2025, the Riverside Sheriff’s Corrections Investigations Bureau began an investigation into members of the public working with inmates to smuggle narcotics into the Cois Byrd Detention Center via the United States Postal Service. During the investigation, Cesar Arenas, a 34-year-old resident of Perris, was identified as the suspect who sent narcotics to a Riverside Sheriff’s Correctional Facility via United States Mail. Dale Thomas, a 41-year-old resident of Temecula, was identified as the inmate to whom the narcotics were sent.

On March 20, 2026, a search warrant was served in the 200 block of W. 2nd Street in the city of Perris. Cesar Arenas was located and taken into custody without incident. During the service of the warrant, a .38 caliber revolver and ammunition were located. It was discovered that Cesar Arenas was a convicted felon and was unlawfully in possession of the firearm and ammunition. Arenas was later booked into the Cois Byrd Detention Center for smuggling narcotics into the jail, conspiracy, and firearm-related offenses. Charges were also filed against Dale Thomas for smuggling narcotics into the jail and conspiracy.

This investigation was part of the Riverside County Sheriff’s Office’s ongoing mission to prevent narcotics from entering our correctional facilities. The diligence of our deputies during searches, implementation of “Jailhouse Mail,” and the nonintrusive sensor and scanning device known as the “OD Security Soter RS,” and comprehensive criminal investigations such as this are among several measures the Riverside County Sheriff’s Office has taken to combat the supply of narcotics into our jail system. Inmate education is a priority within our jails, and inmates are furnished with educational material and classes about the dangers of narcotics, with an emphasis on fentanyl, provided by the Detention Health Services Division of the Riverside University Health System.

This investigation remains ongoing. Anyone with information related to this investigation is encouraged to contact Investigator Arturo Rodriguez at 951-955-6950 or Correctional Deputy Gerald Dye at 951-696-3487.

Reporting Officer: Sergeant Matt Posson

File: SC251690002

Source: Riverside County Sheriff’s Office