Police have received reports of a crash involving up to five cars near Tamahere in Waikato.
They were called to the scene at 12.30pm.
The crash site is approximately 1km south of Tauwhare Rd on the Waikato Expressway in the northbound direction.
A St John spokeswoman said three people had been transported to Waikato Hospital, one in a moderate condition and two with minor injuries.
A Police spokeswoman said one lane remained partially blocked and police were directing traffic at the scene.
Police asked for patience from any traffic that may be using that part of the expressway.
The cause of the crash was not yet known.