More than 300 Civil War-era cannonballs have been unearthed at a construction site in Pittsburgh, PA. So reports the Pittsburgh Post-Gazette.

Many of the cannonballs still contain black powder and are considered a hazard. While the odds of one of these cannonballs exploding is unlikely, a specialist has been called to the site to properly remove the artillery. The construction site is near a middle school.

Read the full article from the Pittsburgh Post-Gazette.