Police are asking people to avoid Riccarton Rd in Christchurch because of concerns about the stability of two commercial buildings.
They say one of the buildings will have to be demolished and the other may lose its facade.
Cordons have been put in place at a number of intersections along Riccarton Rd and traffic queues are growing, so motorists are advised to avoid the area.
One of the buildings is at the intersection of Riccarton Rd, Straven Rd and Clarence Rd. The other is on Riccarton Rd close to its intersection with Rotherham St.
Police say the cordons are likely to be in place for most of Thursday afternoon.