The parents of a toddler who was poisoned by ingesting fentanyl in Northern California have been arrested on child endangerment charges, authorities said.

The parents of the child took their son to a fire station in the town of Concow Monday and told firefighters they feared he had ingested an unknown substance while in someone else’s care, the Butte County Sheriff’s Office said in a statement Tuesday.

“The child was acting lethargic and showing symptoms of opioid poisoning,” the office said.

A helicopter with Enloe Medical Center in nearby Chico flew to the rural community and medics gave naloxone to the child who responded to the overdose medication, authorities said.

The child was flown to Enloe Medical Center in nearby Chico for treatment and has been in the care of professionals from the Butte County Children Services Division since his release, the office said.

Detectives served a search warrant at a trailer where they believe the child ingested fentanyl and found methamphetamine in the home and a small amount of fentanyl in the parents’ vehicle, authorities said.

They arrested the couple on child endangerment and possession of controlled substances charges, the office said.

Also on Monday, three children, ages 9, 11, and 16, who were listed as missing in San Joaquin County last week were found surrounded by methamphetamine and other drugs, authorities said.

Citing “substantial danger to the physical and emotional health,” the San Joaquin County Sheriff’s Office launched a search for the children after their mother failed to turn them over to officials in Stockton after a court order, the sheriff’s office said in a statement.

Deputies pulled over a vehicle with the father and another woman inside on Monday in Stockton and arrested them. Later that day, deputies found the three children inside a Lathrop home along with their mother, who also was arrested, officials said.

The children’s father and mother face charges of child abduction, child abuse, and disobeying a court order, the office said.