A baby injured in a serious head-on collision involving a truck and a car at Thornton, near Whakatane, has died at Auckland's Starship Hospital this morning.

The four-month-old baby and a four-year-old girl were both flown to Starship Hospital after being in a crash on the Thornton Bridge, on Thornton Rd near East Bank Rd and West Bank Rd, about 2pm on Sunday.

The remains of the car involved in the head on collision with a truck on the Thornton Bridge. Photo: supplied.

In total five people were injured in the crash between the car and truck. The car's occupants, the two girls suffering serious injuries and two women, aged 28 and 56-years-old, were taken to Whakatane Hospital in a serious and critical condition.

The 63-year-old man, who was the sole occupant of the truck, only received minor injuries.

St John Territory manager for Eastern Bay of Plenty Richard Waterson says the two girls were airlifted to Auckland's Starship Hospital.

The 28-year-old woman, believed to be the mother, is being transported to Auckland Hospital.

'We had the helicopter and three ambulances there [at the crash scene].”

A Starship Hospital spokesperson says the four-year-old girl is now in a stable condition.

On Sunday police, three fire appliances and paramedics spent a lengthy amount of time working on those injured, with firefighters using the jaws of life on the car to remove the injured occupants.

Trustpower TECT Rescue Helicopter pilot Liam Brettkelly says the four-year-old girl was airlifted to hospital with serious leg injuries and lacerations to her arm and head.

'It appears the driver of the car fell asleep at the wheel, which then collided head on with a small truck,” says Liam.

The Thornton Bridge was blocked for several hours with traffic diverted onto East Bank and West Bank roads.

Eastern Bay of Plenty officer in charge of road policing Seargent Ray Wylie says initial enquiries indicate a motor vehicle travelling east towards Whakatane has crossed the centre line into the path of an oncoming truck.

"There were four occupants in the east-bound vehicle," says Ray. "The driver of the truck has been discharged from Whakatane hospital."

"The serious crash unit is currently investigating the cause of the crash."