Oamaru suddenly became a scene of devastation yesterday after a serious crash left nine people injured.

A witness said there were injured people "everywhere". Emergency services personnel were working frantically to rescue "screaming" people from "mangled" vehicles.

Police rushed to the scene on State Highway 1 at Maheno around 6pm to find people trapped in the vehicles involved.

A northbound Mitsubishi people-mover with six occupants collided with a small, southbound Toyota car containing three people at the intersection of SH1 and Maheno-Kakanui Rd near the Kakanui River bridge.

Sergeant Blair Corlet, of Oamaru, said two people trapped in the Mitsubishi were in a critical condition. They were freed by firefighters using the jaws of life.

Three other occupants received serious injuries, and a fourth had moderate injuries.

The 42-year-old Waimate woman driving the Toyota was seriously injured and her passengers — a 1-year-old baby and a 16-year-old — received moderate injuries.

All were taken to Dunedin Hospital in three rescue helicopters after nine ambulances were sent to the scene.

Initial reports from police said five people were injured in the crash, later correcting that number to nine.

The highway was closed in both directions after the crash, and detours were put in place until the highway reopened about 7.30pm.

Northbound traffic was being diverted at the intersection of Fortification Rd and SH1.

Southbound traffic was also being diverted, at the intersection of Happy Valley Rd and SH1.

Corlet said a Serious Crash Unit from Invercargill was investigating the crash.

Police were still at the scene at 10.30pm last night.

Seven injured in three other road crashes this weekend

• A Mercedes crashed into a tree at Horotiu in the Waikato at 10.45am yesterday, leaving the driver with critical injuries.

• The front-seat passenger had moderate injuries.

• Three people were injured, one seriously, after a tour bus and rental car collided near Christchurch International Airport, at the intersection of Wairakei Rd and Orchard Rd, at 9.15am on Saturday.

• One person had serious injuries and two others were left with moderate injuries, a police spokeswoman said.

• Two people were injured when a car plunged off a bank on State Highway 25 in the Coromandel just after 9am on Saturday.

- additional reporting NZ Herald