Two people have been seriously injured after a car drove off a high rise carpark building in Hamilton.

Police say the incident happened just before midnight when a car crashed off the third floor of a central city Wilson parking building and plummeted to the street below.

Police found the damaged vehicle in Alexander St.

Two people inside the car, a man and woman, were both taken to Waikato Hospital with serious injuries.

Hamilton street cleaner Ricky Ngaronga, who was one of the first to come across the accident, said the car appeared to have reversed off the building.

He said it had plunged boot-first from the carpark's top level and crashed onto a section of verandah, smashing the clear covering before landing on the city street below.

The car then righted itself back onto its wheels.

The Waikato Serious Crash Unit is investigating.