A California mother has been accused of child endangerment after her 3-year-old son died from a fentanyl overdose earlier this year, police said Thursday.

On May 4, police received a call about an unresponsive child who was turning blue and not breathing in a San Luis Obispo home. The fire department began life-saving efforts and took the child to the hospital, but he never regained consciousness and was pronounced dead that evening.

San Luis Obispo police launched an investigation into the child’s death and performed a toxicology report. The results, which arrived in mid-June, indicated that the child had a high level of fentanyl in his system, the police report said.

Police said they learned that the boy’s mother, 30-year-old Jennifer Mae Niemann, was the boy’s primary caregiver and was present when he died. After a months-long investigation, police determined that her “actions allowed access to fentanyl which directly led to the child’s death,” the report said.

Authorities have not yet specified how the child came to ingest the illegal substance.

On Nov. 8, police located Niemann in San Diego and took her into custody. 

She was taken back to San Luis Obispo and booked into the county jail under four charges — child endangerment with great bodily injury, enhancement for causing great bodily injury during a commission of a felony, possession of a controlled substance (methamphetamine) and possession of a controlled substance (fentanyl).

Niemann’s bail is set at $505,000 according to the San Luis Obispo County Sheriff’s Office website.

The Centers for Disease Control and Prevention classifies fentanyl as a synthetic opioid used for treating severe pain — typically in cancer patients. It is 50 to 100 times more potent than morphine.

Recent cases of fentanyl overdoses are most likely the result of illegally-made versions of the opioid, which sell in the illegal drug market, the CDC said. It is often mixed with heroin or cocaine, sometimes without the user’s knowledge, to “increase its euphoric effects,” according to the agency.

Deaths from illegally made fentanyl are on the rise — in 2020, there were 18 times more deaths from illegally-made-opioids than in 2013, the CDC reports.