KANSAS CITY, Mo. (AP) -- Authorities are investigating a package containing white powder that was opened in a mail handling room at the Internal Revenue Service Wednesday morning.

The Kansas City Star reports that two IRS employees were exposed to the package, which was labeled "anthrax." The return address on the package was a prison.

Hazardous materials crews, police, an ambulance, the FBI and U.S Treasury officials are at the scene.

Emergency workers say said the mail room has a separate ventilation system from the rest of the building.

The Kansas City Star: http://www.kcstar.com