Mother says two toddlers found dead inside hot car 'locked themselves in'.

The mother of two toddlers found dead in a hot car claims the children snatched her keys and locked themselves inside the vehicle.

Two-year-old Juliet Ramirez and 16-month-old Cavanaugh Ramirez were found dead inside a locked car on their parent’s property in Weatherford, Texas, on Friday, CNN reports.

Their mother told police the children were playing inside the last time she had seen them on the 35-degree day.

According to Parker County Sheriff's Captain Mark Arnett, the woman searched for her children inside the house before she went outside to find them unconscious in the locked car.

She said she smashed the car window to get to the children, who were then rushed to hospital and shortly after pronounced dead.

The Tarrant County Medical Examiner’s Office has not yet determined the official cause of death, CNN reports.

Captain Arnett said police were investigating to verify the mother's version of events, and while she had not been charged with any criminal offence, they had not ruled out doing so.

"The question is, can a two-year-old open a car door and a two-year-old and a one-year-old climb inside and lock it?" Cpt Arnett said to CNN.

"In the course of the investigation, if charges are warranted, I’m sure the district attorney’s office will bring them."