Police are warning motorists travelling between Tīrau and Cambridge to delay travel if possible.

Emergency services are at the scene of a serious crash.

"About 5pm, police were alerted to a collision involving two vehicles on Taotaoroa Rd, in Karapiro," says a police spokesperson.

"The road was being used to divert traffic following an earlier serious collision on Tirau Rd, State Highway 1.

"Motorists should postpone travel if possible while emergency services respond."