A muscled-up metal detector may one day reveal whether buried objects are unexploded bombs or harmless junk, its U.S. developers say.

Wars around the world have left landscapes littered with unexploded bombs that countries want to dig up and remove, so land can once again be livable for people and used for agriculture, but "it's difficult to distinguish the unexploded bombs from man-made clutter or junk," Eugene Lavely of BAE Systems in Burlington, Mass., said.

Lavely and his fellow researchers have been working to perfect a technique called time-domain electromagnetic induction to separate risks from rubbish, NewScientists.com reported Monday.

Like "a fancy metal detector," Lavely told an American Physical Society meeting in Boston, it uses a coil to send an electromagnetic pulse 50 feet into the ground.

Objects hit by the waves reverberate like a struck drum and the researchers say they can identify the reverberation signal of a torpedo-shaped metal object with a hollow core that could contain explosives.

Work is ongoing to refine the method to be accurate enough to meet U.S. standards that call for 99.9 percent confidence all bombs have been dug up before land can be declared safe, the researchers said.