Topeka ? Authorities on Monday were investigating the deaths of two 3-year-olds who were found dead inside a car in a south Topeka neighborhood.

Shawnee County Undersheriff Scott Holladay said the children were discovered in a four-door car in the family’s driveway Sunday afternoon, about two hours after their mother first noticed her son and daughter were missing. He said authorities were treating them as unattended deaths and had not yet determined how the children ended up in the car.

“This is a tragedy for everyone involved,” Holladay said.

The Shawnee County coroner was conducting autopsies, and Holladay said it could be several days before more information is available. The names of the children and their parents were not released.

Holladay said the mother “was very distraught, as would be expected, both her and her husband, from the loss they had suffered.”

According to a timeline established by the sheriff’s office, the mother noticed the children were missing after 1 p.m. She searched for the two in another vehicle that was parked on the curb in front of the home. She reported the children missing at 2:05 p.m., with the first deputy arriving 10 minutes later.

“Certainly, at this point, we wish that that car was the very first place that we looked, but it was not,” Holladay said, noting that the mother had told authorities that she had looked in her car and they didn’t realize she hadn’t checked the car in the driveway.

The children’s father was at work at the time, Holladay said.

By 2:50 p.m., seven deputies were involved in the search, Holladay said. At 3:14 p.m., a deputy discovered the children in the car parked in the driveway next to a boat. One child was on the driver’s side floor in the front seat; the other was lying on the back seat, he said.

The car was in the driveway leading up to the home, he said, but the children were not in a position that would have been noticeable by someone walking by unless the person stopped to look inside.

The girl, who was born Sept. 29, 2004, was pronounced dead at the scene. The boy, born Aug. 2, 2005, was transported to a Topeka hospital and pronounced dead at 4:16 p.m.

The temperature Sunday afternoon was about 75 degrees, but officers said it could have been 20 to 30 degrees warmer in the car with its windows up.