Des Moines firefighters were called to the Des Moines Register building in the downtown area of the capital city just after 10 this morning. A fire department spokesman says a letter was opened that contained a granular substance and three employees were contaminated. HZAMAT crews shut down a busy city block and erected a large blue tent to wash down the employees as a precaution. Part of the multi-story building was also evacuated.Officials say they’ll run tests to try and identify the substance.