UPDATED 3am Tuesday: Police are asking for witnesses of a crash on SH33 south of Paengaroa that has left a man with critical injuries.

Highway patrol sergeant Mike Owen says a white Toyota saloon travelling north on State Highway 33 collided with a silver Holden vehicle heading south; at about 5:30pm on Monday.

Two male occupants of the Toyota and the female in the Holden were all taken to Tauranga Hospital.

The 33 year old male passenger in the Toyota has suffered multiple head, chest, torso, pelvic and leg injuries and is in a critical condition.

The 27 year old male driver of the Toyota has suffered minor leg injuries.

The 18 year old female driver of the Holden has sustained minor head injuries.

Diversions were in place for about 3½ hours while emergency services attended the scene. Police Serious Crash Unit attended and investigations are continuing into the cause of the crash.

Police would like anyone who witnessed the crash, or who saw either vehicle on SH33 around the time crash to contact Tauranga Police on 577 4300.

UPDATED 6.12PM: A person who is in critical condition is being cut from a vehicle on State Highway 33, following a head-on crash just after 5.30pm.

Emergency services are at the scene on State Highway 33, just past Allport Road.

Northern Fire Communications shift manager Colin Underdown says firefighters are working on freeing the man.

"Another male is on the side of the road and another man is in serious condition.

"I understand police have diversions in place."

It's unclear how the crash happened, but the serious crash unit has been called to investigate.

Motorists are being asked to avoid the area if possible, or expect delays are they are diverted around the scene.

Witnesses to the crash can report any information to Tauranga Police Station on 07 577 4300.

Alternatively, information can be left anonymously via the Crimestoppers 0800 555 111 line.

Earlier:

It's understood one person is in critical condition and another is in serious condition.

People are being asked to avoid the area if possible or expect delays.

Diversions are being set up at Paengaroa and Maniatutu Road.

SunLive will bring you more information as soon as it is available.