A 9-year-old boy was killed after the vehicle he was a passenger in was swept away in a Mid-Canterbury river and rolled, trapping him inside.
The boy was with three adult males when their vehicle got into trouble in the Clyde River at about 10am.
The river is in the Ashburton Lakes area.
Garden City Helicopters general manager Simon Duncan said a personal locator beacon was set off after the vehicle "had been swept away and rolled several times downstream".
The boy, believed to be from Christchurch, was trapped inside and died.
Duncan said three adult males were airlifted back to Christchurch with minor injuries.
They underwent medical checks before speaking to police about the fatal incident.
Police said the Serious Crash Unit was investigating.
The boy's name has yet to be released.
The Ashburton Lakes area is about two hours inland from Christchurch.
Lake Clearwater, Lake Camp, Lake Denny, Lake Emily, Lake Emma, Lake Heron, Lake Roundabout, Lake Spider and two small lakes are situated in the region.
Emergency services rushed to Peachgrove Rd at 4.40am.