In the first part of December, the number of fatal overdoses in Plymouth County spiked to its highest point of any month in 2022.

There were 13 fatal overdoses from Dec. 1 to 19, according to the county’s 27 police chiefs and the organization Plymouth County Outreach, which works to reduce overdose fatalities and support addicts and their families. That compares to seven in the entire month of December in 2021.

Plymouth County Outreach issued an alert to make people aware of the increased risk.

“Anyone using a substance purchased off the street is at risk of an overdose,’’ the alert said.

The alert cautioned that there is more toxic fentanyl being mixed with substances such as cocaine and street pills marked as Xanax. The animal tranquilizer xylazine also has been increasingly found in the illicit drug supply and is being added to opioids, but does not respond to the overdose-reversing medication Narcan.

The number of fatal overdoses was down 20 percent from Jan. 1 through Nov. 30, 2022 compared to the previous year, according to Vicky Butler, the executive director of Plymouth County Outreach.

Butler said the uptick this December prompted the alert.

“It’s not clustered in any particular area, so it’s hard to pinpoint why the spike is happening,’’ Butler said. “There’s always concerns about non-opioid substances being laced with fentanyl — which is why we encourage people using to test their substances, carry Narcan, and never use alone. The holidays can be a difficult time for people, too.’’

Butler said the 2022 numbers are preliminary, and the final annual report will be released in March.

Plymouth County Outreach is a collaboration of municipal police departments, as well as the Bridgewater State University Police Department, the district attorney’s office, and the county sheriff’s department. The group works with recovery coaches and community organizations to make treatment and resources more easily accessible to people with substance abuse disorders and their loved ones.

“Our goal is to provide compassionate, judgment-free support while reducing overdose fatalities,’’ the group says.

Plymouth County Outreach can be reached at plymouthcountyoutreach.org/connect, or by calling 774-434-5072.

Johanna Seltz can be reached at seltzjohanna@gmail.com.