TACOMA, Wash. -

A 24-year-old mother has been charged with injecting her three children with heroin.
   
The Pierce County Prosecutor's Office says the woman was charged Monday with unlawful delivery of a controlled substance to a person under age 18, criminal mistreatment and child assault.
   
State Child Protective Services investigators became involved after receiving a report of heroin use at the home she shared with the father of their children. He was charged with the same crimes in September.
   
The children ages 6, 4 and 2 were removed from the home in 2015.
   
Child Protective Services investigators say the oldest child told them their parents used a needle to inject him and his sisters with "feel good medicine" and that it put them to sleep.
   
The Washington State Patrol Crime Lab says the 2-year-old's hair follicles tested positive for heroin and that the 4-year-old also had signs of heroin in her system.