By Courtney Sherwood

PORTLAND, Ore. (Reuters) - A group of Oregon children who stumbled across an un-detonated, decades-old military-grade mortar shell in a Portland wildlife refuge took it to a play date but escaped unharmed, Portland police said on Wednesday.

The foot-long (30-cm-long) weapon was likely tossed as refuse into the Oaks Bottom Wildlife Refuge, and officials do not expect to find any more un-detonated bombs in the area, said Portland Police Bureau spokesman Pete Simpson.

"It's a mortar shell and very old. Not clear how old, but certainly decades, at least," Simpson said.

The children who found the dull-green, stout torpedo-shaped explosive carried it about one mile to a local home, at which point an adult called police.

Police officers evacuated several surrounding homes, according to a department press release.

Experts with the 142nd Oregon Air National Explosives Ordinance Disposal Team and a second, local agency, bomb squad worked together to deactivate the object, which was still potentially dangerous, the press release said.

It is rare, but old ordinance is occasionally found around Portland, though usually buried or left underwater, not discarded above ground in areas where children play, according to local officials, who said they doubt there are more mortars at the Oaks Bottom Refuge.

"Community members are asked not to touch or disturb these items, as they can be very dangerous if moved," the Portland Police Bureau said in a statement.

(Reporting by Courtney Sherwood in Portland, Oregon; Editing by Eric M. Johnson and Sandra Maler)