Three North East firefighters were taken to hospital after their appliance overturned last night.
The fire engine, from Stockton fire station, was on its way to an emergency call in Middlesbrough.
No other vehicles were involved.
An investigation is under way into the accident.
Cleveland Fire Brigade issued a statement last night: "Cleveland Fire Brigade confirm that one of its fire engines was involved in a road traffic accident tonight (30/04) at 9pm.
"The fire engine from Stockton Community Fire Station was one of five engines responding to an emergency incident in Middlesbrough.
"The accident occurred on the roundabout at Billingham Bottoms where the vehicle overturned onto its side. No other vehicles were involved.
"On board were five firefighters, two escaped with no injuries whilst three sustained non life-threatening injuries and have been treated at University Hospital of North Tees.
"The welfare of our staff is paramount and an internal inquiry has commenced to determine the cause of the accident."
A North East Ambulance Service spokesman said: "We were called just after 9pm to the scene of a fire engine that had rolled over.
"We sent two ambulances, a hazardous area response team vehicle and a clinical care manager to the scene."