Florida ? A landscaping crew about to grind a tree stump discovered 30 World War II mortar shells buried on property once owned by the Navy.

A worker hit and broke one of the shells Friday, but it did not detonate. The mortars could have done serious damage had they exploded, Sgt. Bobby Randolph of the Monroe County Sheriff’s office said.

As a precaution, about a dozen homes were evacuated and cars were cleared from the area while a bomb squad removed the explosives.

Sheriff’s spokeswoman Becky Herrin said authorities will contact Naval officials to “see if they want to destroy them. If not, we will.”