The owner of a Sayville diner made a potentially explosive discovery in the form of a grenade beneath the floorboards of his business yesterday.

Dimitrios Sioutopoulos, who owns Sayville Modern Diner, says he called a plumber in to check on a gas leak in a crawlspace. Minutes later, the plumber emerged from the cramped confines with a terrified look on his face.

The plumber found what looked like a hand grenade, which he photographed with his cell phone. Sioutopoulos called police, and the arson squad that arrived to remove the explosive confirmed that the grenade was live.

Sioutopoulos says the diner has been in his family since the 1930s, and the grenade turned up next to some relics from the 1940s.

"It's kind of scary actually to think that it could have gone at any minute, and it was right next to the gas line," says waitress Tiffany Popke.

Police say the grenade was taken to a bunker, where it will be destroyed at a later date.