Four people have been injured as a result of a major crash involving a van and truck-and-trailer unit on Matakana Rd, near Warkworth.
An Auckland Westpac Rescue Helicopter spokesman said that the rescue helicopter crew were called to assist in the motor vehicle accident around 12.30pm.
"It appears the vehicle collided with the truck trailer. The truck driver was unharmed.
"There were four patients and we attended to a boy who was in a critical condition," he said.
The boy suffered severe leg injuries and was given whole blood by the crew before he was flown to Starship hospital in a critical condition.
The Auckland District Health Board said as of 5pm on Wednesday the young boy who was flown to Starship was in a stable condition.
The spokesman said that the Northland Emergency Services Trust helicopter also attended the crash.
Police said that two more patients were in a serious condition while another was moderate.
A spokesperson said that police and other emergency crews were still on the scene around 2pm this afternoon.
A Fire and Emergency spokesman said fire crews used rescue gear to reach the trapped victims.
Diversions are in place at Sharp Rd and Matakana Valley Rd.
Police request that motorists be patient and advise that delays should be expected.
The Serious Crash Unit is investigating.