BLYTHEWOOD, S.C. — Twin 20-month-old boys found dead inside a car in the parking lot of a South Carolina day care were likely in the hot SUV for more than nine hours, authorities said Thursday.

A parent discovered the toddlers in rear-facing seats shortly after arriving around 5:40 p.m. Wednesday at the Sunshine House Early Learning Academy on U.S. Highway 21 in the Columbia suburb of Blythewood, investigators said.

Bryson and Brayden McDaniel appeared to have been in the SUV since the morning and likely died from exposure to the heat, Richland County Coroner Nadia Rutherford said at a news conference.

Richland County deputies are investigating the deaths.

Temperatures in Columbia were over 80 degrees for most of a muggy Wednesday in Columbia.

The coroner did not name the parents, saying she did not want to criminalize them if the case was ruled an accident, and would not say where the SUV was for most of the day.