DETROIT -- Two boys waiting for a ride to school were overcome by carbon monoxide on Tuesday morning, Local 4 reported.

The 3- and 10-year-old brothers were left inside a running car parked in a garage outside a home near Mound and Caniff roads on Detroit's east side. Police said the boys' mother started the car to take the children to school, but forgot something inside the house.

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"The mother forgot some papers, ran back inside of the house. During that time, the garage door closed," said Cmdr. Robert Dunlap, of the Detroit police 11th Precinct. "We don't know how the garage door closed and the garage filled with … the exhaust from the vehicle which was running."

The mother reportedly found the boys unconscious when she went back to the car.

The mother and the boys' father carried the children to the front porch and tried to revive them by putting snow and cold rags on their faces, the station reported.

Emergency crews were called to the home and police escorted the ambulance to Children's Hospital.

The boys were later transferred to Detroit Receiving Hospital to undergo hyperbaric oxygen therapy. They were expected to be OK.

Investigators said they do not know how long the children were in the garage with the car running.

The boys' father believes one of his sons hit a remote control, which closed the garage door.