A startling discovery was made Tuesday afternoon by a group of construction workers after a hand grenade detonated in an area where they were digging, according to the Teton County Sheriff’s Office.

It happened just after 2 p.m. bordering Highway 89 near the Jackson Hole Gun Club, Sgt. Todd Stanyon said.

“Our bomb team went in and confirmed there are four or five hand grenades that spilled out of the box,” Stanyon said. “The box was in the ground when it popped.”

The small explosion caused the box and its lid to buckle, Stanyon said. No one was injured and there wasn’t significant property damage, he said.

The box was found about 75 yards and uphill from the highway, just in front of the gun range. It was a few feet underground, Stanyon said.

“It was buried at the foot of a large bush,” Stanyon said.

Bomb technicians with Teton County Sheriff’s Office and the Jackson Police Department examined the box and confirmed the box contained hand grenades. An explosive ordnance disposal team from Hill Air Force Base in Salt Lake City was called and responded Tuesday night.

It’s unknown who the bombs belong to or when the box was buried.

“We think they’ve been there a number of years,” Stanyon said.

If the grenades were homemade or tampered with, a suspect could face a federal charge of manufacturing an explosive device, according to Teton County Sheriff Jim Whalen.

“In terms of charges I believe it would be a federal jurisdiction,” Whalen said, meaning his office would hand the investigation over to the federal government.

Later in the evening Tuesday, law enforcement officers closed the highway intermittently from about 9 p.m. to 11:30 p.m. as experts examined and detonated the explosives.

“We don’t perceive this is a real public safety issue,” Whalen said Tuesday evening, “but we are keeping people away.”