Attorneys for 16 Indiana National Guard soldiers filed suit Wednesday against the largest U.S. contractor working in Iraq, alleging the company knowingly exposed the soldiers to a cancer-causing toxic chemical.

The soldiers filed suit against Houston-based KBR Wednesday in U.S. District Court in Indianapolis. The lawsuit, filed in U.S. District Court in Indianapolis, alleges that the soldiers were exposed to sodium dichromate, one of a number of inorganic compounds containing a highly toxic form of chromium known as hexavalent chromium.

The U.S. soldiers, along with numerous American civilian contractors, were exposed to the chemical at the Qarmat Ali water pumping plant in southern Iraq shortly after the U.S. invasion in 2003.