BOISE, Idaho (AP) — Here's a strange and potentially dangerous coincidence: Twice in the last three days, people in southern Idaho have come across two similar, decades-old artillery rounds in unlikely places. The first 155-mm artillery shell was found Saturday in a field near the Snake River and south of the Mountain Home Air Force Base.

It was later detonated by bomb experts, leaving a crater at the site. The second — also a 155 mm round — was discovered Tuesday in the backyard of a vacant home in Kuna and later determined to be inert. Authorities say the shells could be more than two decades old and are like those that have been used at least since the Vietnam War. But for now, they say where the explosives came from remains a mystery.