An oil spill at a north western Indiana refinery this week.
It happened at BP’s Whiting refinery.
Officials say that an undetermined amount of oil leaked into Lake Michigan.
It happened when oil had entered the refinery’s cooling water system, which discharges into the lake about 20 miles southeast of downtown Chicago.
Wind and oil booms have helped to keep the oil from spreading too far from shore and out into the lake.
Officials are still assessing the extent of the spill and damage to the environment.
It is believed that between 10 and 12 barrels, or around 500 gallons, of crude oil spilled into the lake.