Police are appealing for witnesses to come forward following a serious crash on State Highway 31, near Otorohanga.

Emergency services were called to the scene about 2.55pm on Monday.

One person was seriously injured, while two others sustained moderate injuries, says a police spokesperson.

"One of the vehicles ignited following the crash, and the fire spread quickly to surrounding vegetation.

"Police are looking to speak with anyone who witnessed the manner of driving of the vehicles involved preceding the crash, or anyone who witnessed the crash itself."

Those vehicles are a grey 2019 Volkswagen Tiguan, and a grey-and-white 2018 Fiat Ducato campervan.

Anyone with information should get in touch with Constable Leesa Anderson or Senior Constable Mark Strongman at the Te Awamutu Police on (07) 872 0100.

Information can also be given anonymously through Crimestoppers on 0800 555 111.