Nearly 1,000 fish were found dead in a pond on the National Mall in Washington, D.C., on the evening of Aug. 14, according to the National Park Service.

Carol Johnson, an NPS spokesperson, told ABC News that fish are being removed and the water is getting tested.

"We have no reason to believe it is anything other than environmental conditions," said Johnson.

Johnson said this has happened before, particularly in the summertime, although she could not recall the most recent incident.

"Because of the way [the pond is] constructed it's an ongoing problem," said Johnson. She explained that because the pond is not near a river, it is a closed system and is therefore difficult to keep in ecological balance, which can cause incidents like the death of these fish.

"We have identified it as an area that needs to be worked on," she said.