Maintenance noise that was mistaken for gunfire caused a commotion during the downtown Minneapolis lunch rush Friday, as police spent more than two hours searching an office building filled with Target employees.

Police received a 911 call about 11 a.m. Friday that shots were heard on the upper floors of the Retek building on 10th Street between LaSalle Avenue and Nicollet Mall. Target, which leases office space in the 12-story building, said about 1,300 of its employees and contractors work there.

A public address system warned workers of an "active shooter alert" and advised them to stay in their offices. After a search, however, heavily armed police found no evidence of a shooting.

"There are no victims, no suspects, nothing to indicate that there was in fact shots fired," said acting police Chief Janeé Harteau.

The building was cleared as safe at about 1:20 p.m.

Police later learned that maintenance workers on the upper floors had been using "a construction tool that mimicked the sound of gunfire," according to a news release.

"As always, our primary focus is on the safety and well-being of our team members," Target spokeswoman Molly Snyder said in a statement. "We are thankful for the quick response of the local officers and to our team for their cooperation."

Staff writer Randy Furst contributed to this report. Eric Roper  612-673-1732  Twitter: @StribRoper