The death of a Texas mother whose body was found in her SUV last month with her hungry, thirsty children alive beside her has been ruled a suicide.

A Frisco police statement says the Collin County Medical Examiner's Office has determined that Christine Thi Woo died of a self-inflicted overdose. Her body and her three children were found March 31 in an SUV parked in a Target department store parking lot in the Dallas suburb of McKinney. The woman and children had been missing for three days.

Authorities have said the children — ages 1, 3 and 5 — were examined at a hospital and appeared to be well.

Woo's husband reported his wife and children missing March 29, one day after he had last seen them.