SALT LAKE CITY - A massive wildfire in southern Utah this summer uncovered scattered underground bunkers stocked with guns, grenades and food that were illegally built in the wilderness, authorities said Thursday.

The Iron County Sheriff's Office did not identify the builder of the bunkers or his motivation.

The sheriff's office said in a statement that it has been investigating since the late June fire, and prosecutors will consider filing criminal charges against the man because the bunkers were illegally constructed on government land.

The hideouts were discovered on June 27, when firefighters near the ski resort town of Brian Head heard the popping sound of ammunition exploding.

They discovered a burned cabin and nearby bunker filled with ammunition, food, explosive powder and dozens of toy grenades that had been altered with pipe fittings.

A bomb squad investigated and authorities located a man who lives in the town of Parowan about 20 minutes away, who acknowledged building the bunker and stocking the cabin.

He also told investigators he had seven or eight similar hideouts in the area that he'd built over several years.

The sheriff's office said the suspect is co-operating.

A phone message seeking more details from the sheriff's office was not immediately returned.

The sheriff's office said deputies, along with investigators from the FBI and other agencies, located and dismantled the bunkers and removed the items and ammunition. Authorities had to use helicopters to reach the remote locations.

A small cabin untouched by the wildfire contained two bunk beds, food and water, reading material and other items, along with ammunition.

Authorities said the wildfire, which destroyed 13 homes and cost some $40 million to fight, was sparked by a 61-year-old man burning weeds. He's facing charges for reckless burning and burning without a permit.

The area is in some of the same remote territory where a reclusive survivalist lived in the wilderness and burglarized cabins.

Authorities said Troy James Knapp, nicknamed the "Mountain Man," would stash weapons, dehydrated food and camping gear in the woods. Knapp was arrested in 2013 and is serving what will likely be a 10-year prison term for weapons and burglary charges.

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Associated Press writer Lindsay Whitehurst contributed to this report.

News from © The Associated Press, 2017