A man involved in a horror two-car crash in Auckland that has left a young girl fighting for her life was seen walking around with blood spilling from his forehead, a witness says.

The Herald can also reveal one of the vehicles involved had failed a warrant of fitness just five days ago, according to online records.

Three people were injured - two seriously and one moderately - after the two-car crash on Ti Rakau Dr in Pakuranga about 9.25am on Sunday.

The two cars were a late model black BMW and a 1990 Honda Civic.

One of the crash victims, a child, was understood to be under 10 and left badly hurt.

The Civic was ripped in half and the key Auckland road was closed as the Serious Crash Unit investigated.

Witness Kenneth Lin was out jogging with his wife around 10am when he heard a loud crunch and his wife heard an "explosion".

"We heard a bang while we were out jogging, it sounded like a explosion.

"By the time we reached the scene the guy who was driving the car in two pieces was being helped by a group of cyclists."

The injured man was standing more than 30m from the front half of the Civic, bleeding from the forehead.

He looked distressed as the cyclists had to hold him to calm him down.

Lin and his wife helped with traffic management but left after the scene became too crowded.

As they left, they found the cradle for the BMW's battery on the side of the road, some distance from the wrecked vehicle.

Lin said it looked as though the Civic was turning from Ti Rakau Drive onto Edgewater Drive when it was in a collision with the BMW travelling on Ti Rakau.

The front of the Civic was on Edgewater Drive while the back was on the side of the road on Ti Rakau.

After running the plates of the Honda Civic through carjam.co.nz it was revealed the car failed a warrant of fitness test on May 8, just five days before the crash.

Another crash witness said the child had received significant, life-threatening injuries.

The child - understood to be a girl - is believed to have been a passenger in a BMW and had to be cut from the vehicle.

The driver of the second vehicle, the Honda Civic, is believed to have been thrown from the vehicle.

The witness said he understood one of the vehicles - believed to be the Honda Civic - was "pink-stickered" some days before the crash.

A pink sticker, which directs that the vehicle is not to be driven on a road, may be issued to the driver or owner of a vehicle by an enforcement officer who believes on reasonable grounds that a vehicle is not in a safe condition to be driven on a road.