Four people have been injured in a five-motorcycle pile-up on a long stretch of road in South Auckland.

Crew from the Auckland Westpac Rescue Helicopter treated riders at the scene in Hunua before sending the chopper on to another incident where a man was in critical condition.

The crew was called out at 3.40pm to assist ambulance officers with the motorcycle pile-up which involved five bikes. Four people were treated for various injuries.

Crewman and co-pilot Aaron Knight said when they were at the scene of the crash another call came in to assist a man in Matarangi who had suffered a medical event.

Emergency services attended the scene of the five motorcycle crash in Hunua. Photo / Auckland Rescue Helicopter Trust
Emergency services attended the scene of the five motorcycle crash in Hunua. Photo / Auckland Rescue Helicopter Trust

The chopper was diverted to Matarangi and the injured riders were transported to Middlemore Hospital by road.

The rider transported by ambulance was in a serious condition and had suffered a broken leg.

"This was the right decision to make because this second patient's life was saved as a result," Knight said.

The second patient was flown to Auckland City Hospital.