PORTAGE, Ind. (AP) — A second spill in less than two weeks at a U.S. Steel plant in northwest Indiana sent an oily sheen onto a Lake Michigan tributary, prompting officials to close some nearby lake access as a precaution. The sheen was detected Thursday morning on Burns Waterway outside the U.S. Steel Midwest plant in Portage, about 30 miles east of Chicago. Company spokeswoman Amanda Malkowski says that by 8 p.m. Thursday it was no longer present on the tributary, and an existing boom had contained the sheen in an estimated 120-square-foot area. Indiana Dunes National Park closed some access to the lake Thursday, and Ogden Dunes also shut down access to the lake from its beach. Indiana environmental officials are investigating.