"The bomb was relatively sophisticated and consisted of several components that had the potential to cause considerable damage should it be connected to a power source," a police spokesman said.
The bomb was made with fuel cells which contained flammable gas. They were tied together and put into a metal tube, attached to an electronic ignition system.
Police were reluctant to divulge more information on the makings of the bomb, in a bid to avoid copycats. But it is understood that if it had detonated successfully, it could have created a significant explosion.
Mr Foster said the Defence Force was replicating the device to see whether it would work and what damage it could do.
The alleged bomb-maker was arrested hours later, after he returned to the Pokeno property in a stolen Nissan Terrano 4WD.
The man was arrested after police found him hiding in the toilet.
He is facing a number of charges relating to the bomb, the stolen vehicles and the firearms.
He is also facing charges relating to a number of cannabis plants and possessing utensils used for smoking methamphetamine.
He has appeared in the Pukekohe District Court and was remanded on bail with conditions including a strict curfew. He will reappear in court on October 5.