BISMARCK, N.D. (AP) — A 2015 pipeline spill of liquid natural gas in western North Dakota initially reported as just 10 gallons is at least hundreds of thousands of gallons larger and may take another decade to clean up, state health officials said Tuesday.

Oklahoma-based Oneok Partners LP reported the 10-gallon spill of natural gas liquids, or “condensate,” from a pipeline at its Garden Creek gas plant near Watford City in July 2015. A report by the North Dakota Health Department said “ground around the pipe was saturated with natural gas condensate of an unknown volume.”

State Environmental Quality Chief Dave Glatt said the company reported last October that it had recovered 240,000 gallons of the liquid gas and that cleanup was ongoing.