BILLINGS - Yellowstone Park officials say progress is being made, but that there is still more work to do following a report on the Interagency Bison Management Plan.

The report was compiled by the Government Accountability Office, and faulted federal and state officials for not doing enough to minimize the slaughter of bison that leave the Park. About 1,400 bison have been killed or removed over the last two months as they have migrated in search of food.

The actions are taken to prevent bison from spreading diseases to livestock outside the park. At the same time, the report did note that the plan has been successful in keeping bison away from cattle to prevent the spread of brucellosis.

"We agree with the GAO that we've made some progress, but that we aren't where we'd envisioned we'd be by now, and that we need to continue to work some more to move the plan forward," says Al Nash, spokesman for Yellowstone National Park. Nash says the government agencies involved in the plan will continue to move forward to increase tolerance for bison movement.

Some conservation groups have pointed to the report to support their position that the current management plan isn't working. Dan Brister of the Buffalo Field Campaign says that a significant portion of the herd has been killed this year, and that the impact of those kills needs to be studied. He says that increased tolerance for bison migration has been too slow, and that a new plan with more tolerance for bison movement should be considered.