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Crews have unearthed more than 300 cannonballs at a construction site in Pittsburgh, a public safety official told Fox News. The artillery is believed to be from the Civil War era.

“I don’t believe anyone else has found cannonballs at their construction site so you know we’re all obviously relatively new to this experience," FRANJO Construction Project Coordinator Nick Leonello said.

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Crews originally thought to have found a few dozen cannonballs, but that quickly escalated to hundreds as the unearthing process began.

Leonello said there's black powder in the cannonballs, which he says can be dangerous.

A Maryland-based company specializing in handling explosives is removing the cannonballs over the next few days.

Leonello adds that all parties involved are taking every precaution they can to ensure their safe removal, although he says the likelihood of one exploding is slim.