A big scrub fire that closed State Highway 1 north of Auckland, causing major disruption to motorists, is thought to have been caused by a cigarette butt.
The fire broke out in Dome Valley at 1.30pm on Sunday and took 60 firefighters five hours to contain.
Rodney District Council principal rural fire officer Scott Marchant says firefighters were treating it as suspicious, but after meeting with police on Monday morning decided that was no longer the case.
Mr Marchant says he cannot confirm his suspicion, but believes the fire was probably started by a cigarette butt thrown from a vehicle.