A spill at a U.S. Steel plant in northern Indiana that sent wastewater containing a potentially carcinogenic chemical into a Lake Michigan tributary was apparently caused by a pipe failure, the steelmaker said Wednesday. Tuesday’s spill of an unknown amount of wastewater led to the closure of two beach areas at the scenic Indiana Dunes National Lakeshore and prompted a local water utility to stop drawing water from the lake out of “an abundance of caution,” the U.S. Environmental Protection Agency said. U.S. Steel said a preliminary investigation shows an expansion joint failed Tuesday in a pipe at its Portage,...