An envelope containing a mysterious powder was delivered to the Milwaukee County District Attorney's Office on Monday, prompting hazmat and fire crews to respond and shut down a key intersection near the justice complex.

Milwaukee firefighters and a hazardous materials crew got a call about the package and were sent to the county Safety Building at Eighth and State streets just before 3 p.m.

Deputy District Attorney Kent Lovern issued a statement on the matter:

"A staff member of the office opened a piece of mail containing a white substance. The item was opened in an isolated area of the office. Emergency personnel have responded to the office and no one is suffering any medical impact from the incident."

Lovern is poised to become the new District Attorney next month after winning an unopposed race in November to succeed longtime DA John Chisholm, who did not seek reelection.

It wasn't immediately clear whether the building had to be evacuated.

Police blocked off the intersection of Eighth and State streets to allow officials to investigate. Motorists were being advised to consider other routes heading in and out of the downtown area.

Built in 1929, the Safety Building is one of the older buildings that make up the county's justice complex.

The six-floor building once housed the central police station, the city and county courts, the city and county jails and the County Sheriff's office.