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Twin toddler girls in Georgia died after they were left inside a hot car Thursday, authorities said.

The children were found strapped in a car seat in the rear of a Nissan sport-utility vehicle parked outside a duplex in Carrollton at around 6:30 p.m., and were rushed to a hospital but did not survive, NBC affiliate WXIA reported.

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When police arrived, neighbors were trying to cool the kids down, police said.

"There were some individuals holding the infants in a pool and actually had some ice packs also, what they said attempting to cool the kids off," Carrollton police Capt. Chris Dobbs told the station.

The girls were reported to be 15 months old. The father was being questioned by police, WXIA reported. The children’s mother was reportedly in Atlanta when the incident occurred. The medical examiner will determine a cause of death.

Related: Could New Technology Help Prevent Hot Car Deaths?

Temperature observations at the Carrollton West Georgia Regional Airport in Carroll County ranged from 87 to 91 degrees Thursday afternoon, according to the National Weather Service. The temperature was around 76 degrees at around 8 p.m.

Carrolton is a town of around 24,000 about 45 miles west of Atlanta.

Vehicle-related heatstroke and hyperthermia is the second leading cause of death for children under 14 years old involving cars, the National Highway Traffic Safety Administration said in a 2015 report.

Twenty-five children died of heat stroke involving cars in 2015, down from a spike in 2013, when 44 kids died, according to the advocacy group KidsAndCars.org.

At least 685 children have died of heatstroke related to vehicles in the U.S. since 1998, according to Jan Null of San Jose State University's Department of Meteorology & Climate Science, who tracks hot car deaths.