A serious crash on State Highway 1 at Rakaia has created lengthy delays for motorists.

Emergency services were called to the incident near the intersection with North Rakaia Rd about 1.10pm.

A police spokesperson said there have been injuries reported.

"The Serious Crash Unit have been notified.

"Main South Rd (SH1) around the area is blocked and will be for a significant period of time.

"Motorists are advised to avoid the area and choose alternative routes as emergency services work at the scene."

NZ Transport Agency Waka Kotahi said traffic cameras showed long queues of vehicles leading south on to the Rakaia River Bridge.

"Road users should expect delays, and people are urged to avoid the area if they can," an NZTA spokesperson said.

-Allied Media