Dead fish are no longer lining the banks of the Red River but the investigation continues to find out what's killing them.
Oklahoma Department of Wildlife Conservation officials say three weeks ago, the river banks were full of about 400 dead catfish, buffalo and carp.
And the carcasses started at Ketchum Bluff in Jefferson County and continued downstream for about 20 miles.
So far, wildlife officials say they're ruled out golden algae or any other natural occurrence as the cause.
"We have done a lot of tests on soil and water and the fish themselves to see what we might trace it back to, but we don't have any confirmed data yet," says Larry Cofer, regional fisheries supervisor for the Oklahoma Department of Wildlife Conservation.
Cofer says those tests were taken by the Department of Environmental Quality.
He expects results to be in next week.