FENTON, Mich. -- Authorities said a 7-year-old boy was killed when his motorized dirt bike crashed at a track south of Flint.

Witnesses said the boy lost control of the bike and hit a pole Monday at Fenton Indoor Motocross in Genesee County's Fenton Township.

Tyler Waller died three hours later at Genesys Regional Medical Center.

Sheriff Robert Pickell said he's investigating a 22-minute wait for an ambulance.

A first ambulance six miles away couldn't find the track, then broke down.

Track manager Tommy Barron told The Flint Journal the bike's handlebar apparently hit the boy in the chest.

Barron said there have been other crashes since the track opened in November, none of them serious.