Infant twins in Virginia are dead after the babies were allegedly left alone in an SUV for hours.

Maj. Frank Carpenter with the Chesterfield County Police Department told WKRC that the babies were found unresponsive Thursday in an SUV on Alfalfa Lane, near Jefferson Davis Highway. The babies are believed to have been in cardiac arrest when they were discovered in the car.

According WSET, a baby boy about five or six months old was pronounced dead shortly after the discovery while his twin sister was initially hospitalized in critical condition. She later died.

Neighbors told WSET that the babies’ father first found them in the SUV, and one neighbor said they believed the father forgot the twins were in the car when he arrived home. The babies are believed to have been in the car for several hours.

Maj. Carpenter told WKRC that authorities are treating the deaths as accidental.

A medical examiner is performing autopsies on the babies to determine the precise cause of death.

Authorities have not yet publicly identified the infants or their parents.