7PM: THE 18-month-old boy injured in the crash is tonight in the Intensive Care Unit in the Townsville Hospital with serious head injuries, a hospital spokeswoman said.
UPDATE 4.50PM: BOTH lanes are now open to traffic, a police spokesman said.
UPDATE 2.45PM: A 41-year-old man, a 39-year-old woman, a 17-year-old man and a 4-year-old girl, all from south-west of Mackay died in the traffic crash near Calen this morning.
An 18-month-old boy has been airlifted to Townsville Hospital in a critical condition.
Initial information suggests that a car and a heavy vehicle have collided on the Bruce Highway approximately 10kms north of Calen around 8.30 this morning.
Police have closed the highway in both directions, however one lane is expected to be open within the next hour.
An alternative detour has not been confirmed but the Peak Downs Highway may provide the best alternative route to Townsville.
Motorists are asked to avoid the area if they can.
The Forensic Crash Unit is investigating.
UPDATE: FOUR people have died as the result of crash between a car and a heavy vehicle on the Bruce Hwy, around 10kms north of Calen.
A police spokesman said the crash happened around 8.30am.
A two-year-old boy has been airlifted to Mackay Base Hospital.
A RACQ CQ Rescue spokeswoman said the boy is suffering severe multiple injuries.
A Mackay Base Hospital spokeswoman has said the boy who was airlifted to the hospital is in a critical condition.
The hospital spokeswoman said the boy will be flown to Townsville Hospital this afternoon.
A police spokesman said the Bruce Hwy is expected to remain closed for several hours.
No alternative route to avoid the section of road is available.
He said police have set up road blocks at Calen and at Bloomsbury to the north to stop traffic.
Drivers are being advised they can wait at these locations or return to either Mackay or Proserpine where more services and amenities are available.
EARLIER: Police are at the scene of a major car crash on the Bruce Highway north of Calen.
Initial reports suggest a semi-trailer and four wheel drive collided.
At 8:50am RACQ CQ Rescue made a quick departure to assist with casualties.
It is believed the highway has been blocked and long traffic delays expected.