Officials in Des Moines, Iowa are investigating the discovery of suspicious powder in an envelope addressed to prominent attorney and horse owner Maggi Moss.Haz-mat crews were called to the law firm Tuesday after a letter and a vial of suspicious powder was sent to Moss. Inside was a threatening letter and a small container of unknown powder. Officials say the powder was not dangerous and no one was hurt or contaminated. Officials did not disclose what the letter said.The substance was sent to a lab in Iowa City for further analysis. Officials may find out today what it is.According to a report by one Des Moines television station, Moss believed the incident was related to her horse business and not her law practice.Moss, who ranks among the leading owners in North America this year, was the subject of a profile in the Nov. 20 issue of The Blood-Horse.