An envelope full of feces was sent to the office of state Sen. Lena Taylor, D-Milwaukee.
Taylor spokesman Eric Peterson said the envelope was discovered in the state Capitol mail room Friday morning because of its smell, and staff members alerted him.
The return label read, "Milwaukee Trade Unions Want The Iron Mine."
"We don't know where it came from," Peterson said.
Taylor wrote on Facebook, "I apologize to the Capitol Police and Senate mail staff for having to open and dispose of this incredibly stupid idea someone had."