The crew from Wakari volunteer fire brigade came across a rolled digger on the side of State Highway 1 between Milton and Waihola about 11.30am.
The firefighters were on their way to help with mopping up a fire in Coal Gully Rd near Milton.
A St John spokesman said it were notified of the incident by Fenz and sent an ambulance and a rapid response vehicle to the incident.
One person was taken to Dunedin Hospital with moderate injuries, the spokesman said.