Nisshawn Murphy, 39, was ordered by a court to relinquish her parental rights due to several criminal convictions.
Investigators say the children -- 10-year-old Matisse Murphy, 4-year-old Bryan Murphy and 4-year-old Treasure Murphy -- were taken by their biological mother around 8:50 a.m. on Monday outside of a foster home in Palmdale.
Investigators said Murphy made several trips to the Antelope Valley from South Los Angeles during the past 24 hours.
She is believed to be driving her 2003 white Ford Explorer with the California license plate: 6VZX199.
Palmdale officials had earlier said that an Amber Alert was issued, but they later clarified it was still just a parental abduction.
Anyone with information was asked to contact the Los Angeles County Sheriff's Department Palmdale station at (661) 272-2477.