Mississippi authorities are investigating after a Gulf Coat businessperson fell ill after opening an envelope that contained an unknown substance Tuesday.

Police evacuated the downtown Bay St. Louis business on Court Street after the businessperson went to the hospital after touching the unknown substance.

The person said they opened an envelope at their place and then began to feel ill after several minutes.

Police found the envelope and contacted the Hancock County Emergency Management Agency and Centers for Disease Control and Prevention.

Later Tuesday evening, the police chief told WLOX News that a preliminary investigation by the Mississippi Office Of Homeland Security indicated that no dangerous substances were detected at the office building or in the package.