U.S. Rep. Mark Pocan's district office in Madison and the Marquette University Law School in Milwaukee were among the latest places to receive suspicious mail on Monday, Oct. 19, as similar deliveries were reported at offices around the country.

At Pocan's office near the state Capitol, a staffer recognized an envelope as matching mailings reported elsewhere that contained an unidentified powdery substance. The staffer did not open the envelope, and its contents were sent out for testing. A hazmat crew from the Madison Fire Department responded to the office on Monday afternoon.

Marquette confirmed that a letter consistent with the recent mailings was delivered to campus on Oct. 19, addressed to the Marquette Law School Poll. The university said its police department and the U.S. Postal Service were notified right away, and a Milwaukee Fire Department hazardous materials team assessed the letter. All tests were negative, and the letter was removed from campus.

The two deliveries follow similar reports in Wisconsin last week. U.S. Rep. Gwen Moore confirmed on Oct. 16 that her Milwaukee district office had received mail containing a suspicious substance, and the Wisconsin Elections Commission received a similar piece of mail on Oct. 14. Commission administrator Meagan Wolfe said on Oct. 19 that the substance in that mailing was confirmed to be non-hazardous, and that election officials are trained and prepared for such incidents.

The FBI and the U.S. Postal Inspection Service are investigating a series of suspicious mailings sent to addresses nationwide, including secretaries of state, election offices and congressional offices. The FBI said some of the letters contained an unknown substance, and that investigators are working to identify who sent them.