Twelve people were sent to local hospitals Friday after an employee in Linton Hall received a letter containing an unknown white powder around 2 p.m.

Although no adverse affects from the substance were reported, police officials detoxified the individuals with a bleach solution and ordered a physical examination and potentially some blood work. Employees not exposed to the power were evacuated from the building.

The substance was sent to a Michigan State Police crime lab for testing. MSU Department of Police and Public Safety officials are expecting a conclusion on what the powder is within 48 hours. Cleanup of the building will continue when officials have more information.

MSU police Capt. Dave Trexler said he could not release information about the content of the letter, but police have reason to believe an animal rights group may have sent it.

“We have no evidence to point to one specific group,” Trexler said. “I have no information on why it would be sent to Linton Hall, but we have to treat it as a serious incident. Hopefully it’s not serious.”

At least four police departments as well as the FBI, hazardous materials teams and paramedics were at the hall, which houses the College of Arts and Letters and Graduate School administrative offices.

The Sept. 11 terrorist attacks on New York and Washington have set off fears of bioterrorism. Anthrax, a bacteria that can be put in white powder form, has been causing scares around the country since the death of a Florida man this week. An employee of NBC News in New York received an envelope with an unknown white substance and later contracted skin anthrax. An employee at The New York Times also received such an envelope.

All scheduled homecoming events are set to continue. Mail service also will not be affected.