UPDATED: 4:06pm

Highway is now open in both directions.

Police have released that injuries of the accident victims do not appear to be life threatening.

UPDATED: 1:57pm

It is being reported by motorists on the highway that one lane is now open but Police say major delays expected.

Police are investigating a head on crash involving two vehicles that occurred around 11.30am on the Captain Cook Highway.

Three people sustained serious injuries with two transported by QGAIR Helicopter to Cairns Hospital in a critical condition.

A third person sustained serious injuries and was transported to Cairns Hospital by QAS via road, for treatment.

Police investigators will remain onsite to conduct a number of investigations and arrangements will be made to clear the highway as soon as possible.

The highway is expected to remain closed for at least another hour, however it is likely this closure will be longer.

Motorists held up on the highway are encouraged to make alternate travel arrangements if possible or delay travel.

For those that need to travel, consider taking the longer routes via Julatten or Kuranda Range Roads to avoid the crash site.

All motorists are urged to be patient and drive to the current conditions of the road.

A head-on crash involving two motor vehicles at around 11:45 this morning has resulted in one person being airlifted with critical injuries to Cairns Hospital and the closure of the Captain Cook Highway.

The accident occurred north of Rex Lookout.  

Police have advised that a QGAIR Helicopter transported the person to Cairns Hospital. Police and other emergency services continue to work at the scene in an effort to treat patients, investigate the crash and clear the scene. 

It is unknown at this stage how many other people were involved and whether they were injured. 

The Captain Cook Highway north of Rex Lookout remains closed. 

Further delays are expected. 

Motorists travelling between Wangetti Beach and Port Douglas are urged to avoid travel at this time or make alternate travel arrangements. 

Further updates will be advised.