RED CLIFF, Wis. — Some 22 barrels of military ammunition that were dumped into Lake Superior decades ago have been re-submerged while a local tribe and clean-up workers seek a federal waiver to bring the barrels to shore.

A Duluth News Tribune report says the barrels contain thousands of tiny explosive devices. Each is only as potent as a firecracker, but officials worried that one detonation could cause a serious chain reaction.

Back around 1960, Army ordinance officers ordered the 55-gallon drums secretly tossed into the lake a few miles from shore. Some barrels were later found to have only trace levels of water-polluting chemicals, so officials let them remain.

Officials raised 25 barrels last summer. But they re-submerged the 22 that contained explosives, while they seek a waiver to bring them ashore.