As the officers attempted to stop Morunga fleeing in a white Holden Commodore car, one became pinned by the car and a fence, he said.
The officer suffered minor leg and arm injuries.
Mr Walsh warned Morunga had an "extensive criminal history" and that he should not be approached.
"What we would say to Mr Morunga and any person who may be assisting him is to consider what has occurred and contact police to turn himself in."
Morunga is described as Maori, 176 cm tall and of medium solid build.
Anyone assisting him would also face prosecution, Mr Walsh said.
The second stolen caravan had since been found. It was recovered by Huntly police from a rural location west of the Huntly Power Station following several phone calls from the public.
"Such support is vital for police investigating crime. Sometimes not everyone who would like to help the community can speak directly to police and if you find yourself in such a situation we would encourage you to leave information anonymously with Crimestoppers on 0800 555111."
Anyone with information on Morunga's location should contact Hamilton Central Police Station on 07 858 6200.
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