The US Coast Guard is among the agencies investigating the sheen seen on Lake Michigan at a Region beach on Monday, causing authorities to order swimmers out of the water. National Lakeshore officials say all Indiana Dunes National Lakeshore beaches remain under an advisory until it's determined what it was. The Coast Guard says about 3 p.m. Monday, a communications watchstander at Coast Guard Station Michigan City was notified that people were coming out the water with an oily substance on them at Porter Beach.
The station directed the reporting source to contact the National Response Center, and Coast Guard Marine Safety Unit Chicago dispatched a response boat to the area, and officials say pollution investigators found no visible sheen. Authorities say a helicopter crew from Coast Guard Air Station Traverse City, Michigan, was diverted from a training mission to conduct an overflight of the area from the Port of Indiana to Michigan City, and found no evidence of sheen. They report they did see a few pollen blooms, and that just after 4 p.m., Station Michigan City received a report that the sheen had reached Michigan City. The U.S. Geological Survey has taken water samples, and the results are pending. The Coast Guard also says their investigators are also reviewing a surveillance video provided by the Port of Indiana and have not noticed any signs of pollution.