Two Detroit children who recently died in a van in below-freezing temperatures were victims of carbon monoxide, not exposure to cold weather, authorities said Wednesday.

DETROIT, MI – The Wayne County Medical Examiner’s Office determined the two children found not breathing in a minivan outside Detroit’s Greektown Casino died of carbon monoxide poisoning, Fox 2 Detroit reports. Police originally thought the two children, Darnell Currie Jr., 9, and A’millah Currie, 2, froze to death on Feb. 10.

On Feb. 10, the children's family was parked at the Hollywood Casino at Greektown when their car stopped running in the middle of the night, officials have previously said. Darnell Currie Jr. and A'millah Currie later stopped breathing and died.