A 19-month-old boy has died following an ATV crash Sunday afternoon in Windham, authorities said.

The boy, whose name has not been released, was taken to Maine Medical Center in Portland following the rollover, which was reported before 6 p.m. at 20 Laskey Road. The boy was injured when the ATV operated by his 32-year-old father flipped backward while ascending a hill on their property, according to the Maine Warden Service.

The father was carrying two other children – ages 6 and 4 – on the ATV when the crash occurred, the warden service said in a statement Monday. The boy who died was riding between his father’s legs and the other two children were sitting behind the father on the ATV.

Game wardens say helmets were not being worn by any of the passengers. The ATV was a 2007 Yamaha Big Bear 350.

The injured boy died of his injuries on Monday. His body was to be examined Monday by the state medical examiner’s office.

The warden service has not released the name of the father.

State law says the operator of an ATV is not allowed to carry a passenger under 18 unless the passenger is wearing protective headgear. State law prohibits operating an ATV “in such a way as to recklessly create a substantial risk of serious injury to another person.”

The warden service continues to investigate the circumstances of the boy’s death and will work with the Cumberland County District Attorney’s Office. Windham police and the Cumberland County Sheriff’s Department assisted wardens at the scene.