CLAY COUNTY, Mo. -- Investigators are working to figure out how two young Missouri sisters died on Wednesday after their mother found them unresponsive – neither with any obvious signs of trauma.

The younger sister, 7-week-old Goodknight Berretta June Ribando, was born on Mother’s Day, according to WDAF. Ireland Autumn Jane Ribando was 2 years old.

Clay County investigators say there are no signs of foul play; they declined to give any additional information Thursday morning.

Sheriff's deputies were called to the family's house off of 92 Highway and Cameron Road, just east of Kearney, shortly after noon on Wednesday. When they arrived, they found the sisters unresponsive with no evidence of how they died.

The mother told investigators she went outside and found both girls not breathing, so she picked them up and ran them to the neighbor's house for help.

Officials said there were no apparent physical injuries or evidence of drowning. WDAF reported seeing an SUV on the property with its doors open, and asked investigators if the heat could have caused their deaths, but investigators declined to comment pending full autopsies by the Jackson County Medical Examiner's Office.

Investigators spent the rest of the day on the property executing a search warrant to find whatever clues and evidence they could.

"So far everyone that's involved is working with investigators. There's no reason to believe anyone is trying to hide anything but we know with other situations, we want to make sure no one is lying and make sure we get to the bottom of this," Captain Will Akin said Wednesday.

Investigators say the girls' mother is cooperating and is not a suspect at this time. A GoFundMe has been set up for their funeral expenses.