LINDEN, Iowa (AP) — A central Iowa swine facility has started to clean up after 1,000 gallons of manure was released into a stream.

The Iowa Department of Natural Resources said Tuesday that employees of Carstens Livestock discovered the leak from a manure storage structure Monday outside the city of Linden in Dallas County.

Officials say an emergency shutoff valve failed, allowing the manure to spill into a ravine which runs into a tributary of the Middle Raccoon River.

Of the 1,000 gallons, officials say about 500 gallons were spilled into the tributary. The department says Carstens quickly reported the spill and continued cleanup efforts on Tuesday.

The department says the spill is under investigation.