CHICAGO (CBS) — The Bubbly Creek section of the Chicago River has been closed, after an oil spill was reported in the water.

The spill was spotted in the south fork of the Chicago River on Wednesday in the Bridgeport neighborhood near Ashland Avenue. The sheen of dark oil later spread from Bubbly Creek to the river’s South Branch, as far west as Pulaski Road.

The U.S. Coast Guard and Environmental Protection Agency responded, and closed off access to Bubbly Creek on Thursday. A containment boom was set up at the entrance of the creek.

Officials said crews could be working in the area for weeks. Crews have not yet found the source of the spill.

So far no fish kills have been reported, but some birds have been affected, including ducks, geese, and at least one blue heron that have been covered in black oil.

“We’re working on getting some of the geese collected and cleaned,” said EPA coordinator Len Zintak.

Zintak estimated that at least hundreds of gallons of oil either leaked or were dumped into Bubbly Creek. He called it a large spill, but said he is confident his team can collect most of the oil by next week using absorbent booms.

“That’s going to be the main approach to it now, is using absorbents; and we’ll see if we need to bring in an oil skimmer and vacuum truck,” Zintak said.

The St. Ignatius crew team, which trains on Bubbly Creek, has been told they must move their training to dry land until the oil slick has been cleaned up.

St. Ignatius girls crew coach Len Richards said the team noticed the oil slick while practicing on Monday and Tuesday, because their boats were greasy after pulling them out of the water.

“It was pretty messy. It got messier. So, on Wednesday, we have hoses, we were brushing them off, and wiping them down,” he said. “I mean, we’ve been rowing in it for four days now.”

Richards said the team won’t be able to practice for its last regatta on Sunday.

“It’s nicer to get the live training out on the water,” he said.

The no-boating zone set up by the Coast Guard doesn’t affect the South Branch or other area waterways.