(Yuba-Sutter, CA) — The California Department of Justice confirmed that an envelope sent to the Yuba County Elections office earlier this month did not contain a controlled substance, despite earlier claims by the county that it contained fentanyl.

According to The Appeal-Democrat, On Jan. 16, Yuba County officials said an envelope that was sent from a “verified sender” to the county’s Elections Department contained a “powder substance” that tested positive for fentanyl, a deadly opioid that has led to thousands of deaths in recent years.

Officials with Yuba County previously said a field test of the substance mailed to the Elections Department was conducted by the Yuba County Sheriff’s Office. That testing confirmed the substance was fentanyl, but the Department of Justice on Thursday said secondary testing came back negative for controlled substances.

The incident remains under investigation by the Yuba County Sheriff’s Office.