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Government officials shut down the science building at Inver Hills Community College for much of the day Tuesday after a "harassing" letter arrived with an unidentified dark powder in the envelope, police said.

"Basically, all we were able to determine right now was that it is not hazardous," said Inver Grove Heights Police Lt. Sean Folmar, adding that the state Health Department is performing further tests.

As part of the police response, the 55th Civilian Support Team, a function of the Minnesota National Guard, quickly sealed off the building and limited people's exposure to the room where the letter was opened. That team later determined that the dark brown powder was not chemically, biologically or radiologically hazardous, Folmar said.

Classes were not in session because of the summer break.

Inver Grove Heights police were called to the school just off Hwy. 52 and E. 80th Street at 10:21 a.m. after an employee opened the letter, which apparently was intended for someone else, possibly on the faculty. Police were not disclosing further details, and they have been working with the FBI because the letter came through the U.S. mail, Folmar said.

Police had not identified any suspects by Tuesday evening, he said.

Even if the dark powder turns out to be harmless, the sender could face serious charges, Folmar said. "Just the harassment itself is a criminal offense," he said.

JOY POWELL