The mailroom supervisor at a federal prison in Atwater died Friday, as a result of exposure to mail saturated in an unknown substance. A second worker was also exposed and hospitalized, but released after observation.
Investigators are examining whether the substance was fentanyl, according to the Associated Press.
A spokeswoman for the U.S. Bureau of Prisons, Kristie Breshears, director of communications, confirmed an investigation was underway, but declined to disclose specifics.
The prison, which is located in Merced County, has temporarily suspended visiting.
Atwater is a high-security federal prison for men. It also includes a minimum-security satellite camp. According to the prison’s website, there are 1,225 inmates on its campus — 1,086 are in the prison, and 139 in the camp.
Marc Fischer, the mailroom supervisor, “began feeling unwell” after being exposed to an item of mail, according to Breshears. “Despite the swift response from local emergency medical services, the employee was tragically pronounced deceased upon arrival at the local hospital.”