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JEFFERSON COUNTY, Mo. – Yard work turned into a dangerous discovery for a Missouri woman over the weekend.

Pamela Coffey and her husband moved onto their Grubville, Missouri, property a year-and-a-half ago. Since then they’ve been fixing up the place.

She was doing yard work Saturday when she noticed a piece of metal poking out of the ground. She shared on Facebook that she took it inside and washed it and her husband tried scraping off the dirt with a knife.

They called police, who showed up with bomb and arson investigators. Coffey shared the experience on Facebook and commented that her driveway ended up looking like a crime scene because so many officers responded.

After examining the shell, the Coffeys and officers determined it was a Japanese mortar from WWII.

The department used a robot to collect the mortar from the driveway so it could be x-rayed. An Explosive Ordnance Disposal unit then transported it to Scott Air Force Base. The Mortar was eventually detonated.

Coffey said she’s found curtain rods, fossils and all kinds of other things on the property, but said the mortar shell was the strangest yet. Officers agreed and told Coffey that it was a rare find and they were lucky they found it before excavation started on the property.