CHICAGO — Crews are working to contain and clean up oil that was found on part of the south branch of the Chicago River and a waterway that connects with the river.

The U.S. Coast Guard says it closed off access to the waterway known as Bubbly Creek on Thursday after an “oil discharge” was found in the area. The U.S. Environmental Protection Agency also responded and officials are working to find the source of the oil.

Crews used booms at the entrance to Bubbly Creek to work to contain the oil.

The Coast Guard established a safety zone, closing Bubbly Creek to people and vessels. The agency says the south branch of the Chicago River and other area waterways aren’t affected by the closing.