WILLISTON, N.D. (KXNET) — Zavanna LLC notified the North Dakota Department of Environmental Quality of a produced water spill from a pipeline line they operate in Williams County on Monday.

According to the North Dakota Environmental Quality, the incident occurred about seven miles northeast of Williston.

The cause of the spill is under investigation.

Zavanna estimates that 9,800 barrels (411,600 gallons) of produced water were released. An unknown amount entered Stony Creek.

“It’s salt. Salt tends to flush through a creek, but can bind up into soil. It is detrimental to aquatic wildlife, is our biggest concern on something like that. We have seen some fish killed in the creek. Mostly minnows and stuff like that,” said Bil Suess, spill investigation program manager for the North Dakota Department of Environmental Quality.

Bill Suess, Spill Investigation Program Manager, ND Dept of Environmental Quality)

Produced water is a by-product of oil production.

Personnel from Environmental Quality are inspecting the site and will continue to monitor the investigation and cleanup.