Police spent their last day sifting through a survivalist's home, once filled with improvised explosive devices, firearms and chemicals, trying to figure out how the dangerous items first got into the house.

Barrie Police Const. Angela Butler said investigators are looking for paperwork that could shed light on how the hazardous materials and weapons were obtained as police wrap up their search of the 30 Virgilwood Cres. home in the city's north end.

Any documents, such as permits, found by the officers picking through the two-storey property will help shape expected charges related to the dangerous materials strewn about the home, its yard and an underground bunker, she said.

"They're looking at any kind of documentation in the house that would support anything for firearms or explosives charges."

"It's basically a paper trail at this point," Butler said.

The property was deemed clear of danger on Saturday after dozens of officers from local, provincial and federal police agencies worked with a bomb disposal robot to remove 83 explosive devices, 29 firearms and a quantity of chemicals from the residence.

Once police leave the property Monday, city inspectors can move in and review it for possible bylaw violations — which the city has said could result in the home being demolished, Butler said.

Police had initially declared the house and surrounding area safe Thursday, bringing the search and a week-long evacuation of nearly 60 nearby residents to a close.

However, a tip from homeowner William Feldhoff, 75, led police back into the home's basement on Friday.

There police found yet another cache of chemicals hidden behind a wall panel, leading them to ask people living in four nearby homes to once again leave for the day.

It was the latest twist in the story of Feldhoff, his 54-year-old son Donald and of the residence itself.

Feldhoff has been charged with accessory after the fact in the 1978 cold-case homicide of Michael Traynor.

That development came hours after the July 11 arrest of Feldhoff's son Donald on a first-degree murder charge in the case.

It also led police to check out the residence, where Feldhoff's son had been occasionally living, said Bernard Cugelman, lawyer for the elder Feldhoff.

The property includes a two-room bunker dug into the backyard with a city permit in 1984. Police photos show the space crammed with boxes and jugs of liquid, while Cugelman said the shelter had been "relatively dormant" since being built.

Cugelman said Feldhoff is a survivalist motivated in part by his childhood experience living through devastating bombings of the German city of Dusseldorf in the final years of the Second World War.

He said like other survivalists, Feldhoff is "somebody who, as a result of chapters in the Bible and as a result of world events, believes that the world is heading on a course where we're liable to experience a breakdown of what we take for granted in civil society."

"And so people take steps to protect themselves," Cugelman said, adding that even big-box stores now sell products aimed at those looking to stock a shelter space to ride out perceived uncertainty.

"They sell boxes of survival foods and gear in Costco, so it's gone mainstream. There's a lot of people concerned about the state of the world."