Two toddlers were found dead in a locked vehicle on Friday in Parker County, Texas.

Temperatures had hit 96F (35C) when the mother of the children, a two-year-old girl and a 16-month-old boy, says she found them locked inside her car, according to a news release from the local sheriff’s office.

The Tarrant County Medical Examiner’s website identifies the two children as Juliet and Cavanaugh Ramirez – and says the cause of their deaths is still pending.

Parker County Sheriff’s Captain Mark Arnett told CNN the mother of the two children said they had been playing in a back room of their family home when they disappeared.

After searching the home, the mother says she eventually found the two children locked inside her car, with one of them holding her mobile phone and car keys.

The mother said she broke a window to reach her children, but both were unresponsive by the time she got to them.

“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?” Captain Arnett said.

“In the course of the investigation, if charges are warranted, I’m sure the district attorney’s office will bring them,” he added. So far, no charges have been laid.

“This case is in the early stages of the investigation,” Sheriff Larry Fowler said in the news release.