PORTAGE, Ind. (AP) – U.S. Steel says a failed pipe apparently caused a spill at the company’s northern Indiana facility that sent a potentially carcinogenic chemical into a Lake Michigan tributary.

The company said Wednesday its preliminary investigation shows an expansion joint failed in that pipe Tuesday at its Portage, Indiana, plant.

The steelmaker says that allowed wastewater from an electroplating treatment process that contains hexavalent chromium to flow into the wrong wastewater treatment plant and eventually enter Burns Waterway through a drainage pipe.

The U.S. Environmental Protection Agency says the wastewater entered the waterway about 100 yards from Lake Michigan, but so far no hexavalent chromium has been detected in the lake. It’s also unclear how much of the toxic wastewater spilled.

U.S. Steel says it’s idled all production processes at the facility.