BEIJING, May 9 (Xinhuanet) -- Six lions reported shot to death in traps near a Columbia River dam in the United States died from other, unknown causes, federal officials said Wednesday.

    Federal fisheries spokesman Brian Gorman in Seattle, Washington, said preliminary results of a necropsy found no evidence of recent gunshot wounds but found shallow puncture wounds in one of the protected animals consistent with sea lion bite marks.

    The fisheries department is still trying to determine how the animals died and how the doors to the traps in which they were found had been closed, he said.

    Because the first examination turned up no slugs, investigators had believed the animals were shot at close range with high-powered rifles, the bullets passing through the flesh.

    X-rays on Tuesday found metal fragments in soft tissue near the neck of two animals, Gorman said. A metal slug was found in the blubber of one animal. But neither the fragments nor the slug appear to have caused fatal wounds and may have been from old injuries, he said.

    The sea lions included two endangered Steller sea lions and one California sea lion pup.

    The Humane Society of the United States, which is suing to block the authorized killing or removal of up to 85 animals a year for five years, agreed Tuesday with the federal government and the states of Oregon and Washington to continue a ban on killing and stop the animals' permanent removal until next year.

    The move was in part to allow more efforts to go toward investigating what was thought to be shooting of the animals over the weekend. The agreement allowed the governments to continue removing animals and branding them for identification if they return them to their natural habitat.

    (Agencies)