PHOENIX – The 51-year-old man accused of storing 30 pipe bombs in his Arizona home told law enforcement he began building them on the instructions of his estranged "prepper" wife who feared the collapse of the government.

Jeffrey Metcalf was arrested Thursday on suspicion of making pipe bombs out of his home over the course of four years, according to Maricopa County court records released Friday.

Officials said a DPS task force found 42 pipe bombs in his home with enough raw materials to make at least 30 more. Metcalf took extra steps, including adding shrapnel and sealing the end caps, to make the device more lethal.

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This wasn't the first time Metcalf had been caught with explosives, according to the probable cause statement filed in court documents. He was investigated in 2008 for making an imitation improvised explosive device while he was in the U.S. Marine Corps. Metcalf allegedly told investigators he built the IED to show how easy they were to make.

Uncovering the bombs

The task force, which included Phoenix police and the Bureau of Alcohol, Tobacco, Firearms and Explosives, first learned Metcalf was making and storing pipe bombs Tuesday, according to the probable cause statement. However, they didn't know where the explosives were hidden.

A GPS tracking device was placed on Metcalf's car Wednesday so law enforcement could discreetly follow his movements in an attempt to figure out where the bombs were being stored, the statement said. An undercover surveillance team spotted Metcalf loading black containers, gun cases and duffel bags into the back of his car outside of a Mesa apartment complex. He then headed to his homes.

A DPS trooper pulled Metcalf over a few hours later after he left his home, the report said. Metcalf admitted to storing "several" pipe bombs in his garage when confronted about the explosives. Pipe bomb making components were found in the trunk of his car and 42 pipe bombs were found at his home. Approximately 7,600 rounds of ammunition were also found.

Metcalf speaks to authorities

He told authorities he made the pipe bombs in his home over four years at the request of his estranged wife, who he described as a "ultra-prepper" who feared the collapse of the U.S. Government, the statement said. He moved the bombs to his Payson home three years ago before bringing them back to Mesa in February.

Additional pipe bombs were stored with the person who lived in the apartment complex, the statement said. Metcalf told investigators his friend knew what he was storing and the pair had considered taking the pipe bombs to the desert to blow them up.

He went into great detail explaining how to assemble and handle the pipe bombs to keep it from accidentally detonating, the statement continued. He also told task force members about experimenting with different fusing systems, sealing the end caps to make them more lethal and using an electrical system to detonate the explosives remotely.

Task force members later discovered Metcalf added shrapnel to the devices to make them even more deadly, officials wrote in the statement.

DPS Director Frank Milstead said on Twitter Friday they are still not sure what Metcalf planned to do with the weapons.

ATF and Mesa police evacuated eight surrounding homes before the explosives were removed, officials said. The removal process took eight technicians more than three hours to remove the devices and transport them to a safe disposal location. The "method of construction" forced the technicians to use explosive countermeasures to safely disassemble the bombs.

Metcalf was booked on 40 counts of manufacturing and possessing prohibited weapons. He was being held in a Maricopa County jail on a $50,000 cash-only bail, according to the records.