A Santa Rosa woman was arrested on Tuesday on suspicion of causing a drug overdose in her 1-year-old toddler, the police department said on Wednesday.

At 5:17 a.m. on Tuesday, Santa Rosa Police officers were sent to a residence on Boyd Street for a toddler who was experiencing a medical emergency.

When an officer arrived, he found a 1-year-old lying on the ground, unconscious and not breathing, police said. The officer saw an individual attempting CPR on the child and took over the CPR himself, police said.

After about 15-20 seconds, the toddler began to breathe on her own. By then, emergency medical services arrived and transported the child to a local hospital.

Based on interviews and evidence obtained during the investigation, detectives believe that the toddler overdosed from exposure to fentanyl. The child is expected to recover.

The toddler's mother, a 39-year-old Santa Rosa resident, was arrested on suspicion of felony child abuse with serious injury.

The Santa Rosa Police Department said this was the third fentanyl-related overdose of a child that the department had seen in 12 months.

"Illegal use of fentanyl is dangerous for adults to consume and lethal for children," said a spokesperson from the department. "Two milligrams are considered a lethal dose of fentanyl for an adult."

In the neighboring counties of San Francisco, San Mateo, Alameda, Santa Clara and Marin, nearly 60% of all drug overdose deaths involved fentanyl last year, new data shows.

San Francisco remains the epicenter of the crisis, where a preliminary count of fatal overdoses from January through April shows ODs killed 268 people versus 196 over the same period last year. If overdoses continue at this rate, San Francisco will see its deadliest overdose year ever.