A 9-month-old boy died after his father found him inside a hot car on a Florida driveway, authorities said.
The baby, Keyton O'Callaghan, who had been in the care of his mother, Cami Lee Moyer, since Thursday night, was found in the car by his father, Eric O'Callaghan, on Friday, the Hernando County Sheriff's Office said.
A call was made to 911 around 11:15 a.m. Friday and O'Callaghan performed CPR until first responders arrived at the Spring Hill home and took over, the sheriff's office said.
Keyton was hospitalized in critical condition. He was pronounced dead shortly after noon on Friday, the sheriff's office said.
(MORE: 'This too can happen to you': Heartbroken mother urges parents to prevent hot car deaths)Investigators were "unable to provide a definitive answer to" how long the baby was in the car, the sheriff's office said Monday.
No one has been charged at this time, sheriff's office spokeswoman Denise Moloney said.
Once detectives have completed the investigation, the case will be turned over to the office of the state attorney, the sheriff's office said.
The temperature reached 93 degrees in Spring Hill on Thursday and 94 degrees on Friday. The heat index -- or what it feels like -- reached 103 degrees the day Keyton was found.
At least 35 children have died from hot cars this year in the United States, according to the organization KidsandCars.org.
(MORE: 'Forgotten Baby Syndrome': A parent’s nightmare of hot car death)This is also the third hot car death this year in Florida, the organization said.
ABC News' Rachel Katz and Sam Wnek contributed to this report.