MEAD, Neb. (AP) — A report by state environmental officials says a frozen underground pipe that burst last week likely spilled 4 million gallons of wastewater from a troubled ethanol plant in eastern Nebraska.

The Nebraska Department of Environment and Energy says officials with the AltEn ethanol plant near Mead has submitted a plan to clean up the spill.

Plant officials reported the accidental discharge on Feb. 12 that happened after a frozen pipe on the side of a large digester tank burst, releasing manure from the nearby feedlot and thin stillage from the ethanol plant.

Because the plant uses treated seed instead of harvested grain, it’s likely the thin stillage is contaminated with pesticides, which have been detected in the plant’s lagoons and other waste byproducts at high concentrations.