The coroner who performed the autopsies on two Georgia toddlers who were found dead said Tuesday the children had drowned.

Warren County Coroner Paul M. Lowe said the bodies showed "no signs of trauma" or foul play, but he added that police were still investigating to see if the drownings were accidental.

The bodies of Jonah and Nicole Payne (search), 3 and 2, were found about 12:15 p.m. Monday just a few hundred yards from their lakeside house, according to Georgia Bureau of Investigation (search) spokesman John Bankhead.

A road from the house the children lived in with their parents leads directly to the 1½-acre, bacteria-filled sanitation pond where their bodies were discovered, he added.

Green algae had made it difficult to see the children when authorities first searched the pond over the weekend, Bankhead said, but a second look Monday revealed a bulge in the algae that turned out to be one of the toddler's bodies. The other was found nearby.

"It was very difficult to see these kids. When we first looked at it, we didn't know they were bodies," Bankhead said.

The pond — part of the city's sanitation system — is surrounded by a fence. But the fence has several holes where a child could easily get through.

Authorities said Nicole needed a breathing machine daily and her brother was on medication for an unspecified condition.

The children were reported missing Saturday evening after last being seen at their Warren County (search) home, in east Georgia about 100 miles from Atlanta.

Authorities continued their investigation, reinterviewing family members and neighbors.

"The parents are still very much in shock and mourning," said family spokesman Jaye Jones. "They are only able to speak for a couple minutes at a time before being overcome with tears and sobbing."

The mother, Lottie Kain, had told police she was in another room Saturday and emerged to find the front door open and the tiny siblings missing. She reported their disappearance to authorities early Saturday evening.

Earlier the same day, the little girl had managed to unlock the locked door and escape with her brother about 4 p.m. but a neighbor found the toddlers and they were returned a half hour later, according to Police Chief Jim McClain. Nicole had figured out how to unlock the front door and would do it when no one was around, he said.

FOX News' Jonathan Serrie, Catherine Donaldson-Evans and The Associated Press contributed to this report.