He said they were not injured.
St John Lakes area territorial manager Hilary Morrish Allen said there were seven patients being treated for minor injuries.
Ella Berryman from NZ River Jet which is on the corner of State Highway 5 and Tutukau Rd said she heard a car screech on the road but didn't see what happened.
She said she could see a few cars and a campervan were involved in the crash.
"It's quite scary, I don't know how bad it is."
Owen Johnston, the driver of the camper-van, said it all happened so quickly.
"I didn't have a chance to do anything, it was all over in a few seconds," he said.
Mr Johnston said his wife Judy was a bit shaken up, but neither were injured. They were the only passengers in the camper-van.