Senior Sergeant Anthony Bond, of Dunedin, said officers responded to the incident about 4.30pm.
The truck was being driven on Silverstream Valley Rd and moved to the far left as a car approached in the opposite direction. The truck tipped over, fully blocking road.
No injuries were reported, Snr Sgt Bond said.
The truck was carrying sound equipment for a concert at the Waiora Scout Camp, understood to be the Whare Flat Folk Festival.
Festival organizer Stephen Stedman described the incident as a "low speed tip over".
Nobody was hurt, which had been the main concern of the team running the festival.
The festival was would not be not affected and Mr Stedman was looking forward to a special event with an ideal weather forecast.