Los Angeles police said around 4 p.m. Thursday, Crystal Juarez, 28, took her son and two daughters from her ex-husband's home without permission. The father has full custody of the kids and Juarez was only authorized to visit the children on the weekends.
Authorities said she has family in Tijuana, Mexico, and that she may have taken the children there.
She is described as 5 feet 6 inches tall, weighing 180 pounds. She has a tattoo on the back of her neck of "Humphrey Park."
Her three children are named Gabriel Vargas, 10, Ruby Vargas, 7, and Lily Vargas, 6. Gabriel is described as 4 feet fall, 80 pounds and was last seen in a black shirt and shorts.
Ruby is 3 feet 6 inches, 60 pounds and was last seen wearing a blue blouse, jeans and Spider-Man shoes. Lily is 3 feet 4 inches, 50 pounds and was last seen wearing a white shirt, zebra print pants and pink shoes.
Authorities did not issue an Amber Alert because there was no vehicle description or information.
Anyone with more information is urged to call the LAPD Van Nuys division detective desk at (818) 374-0040. Those wishing to remain anonymous may call Crime Stoppers at (800) 222-8477.