-- An explosion on Saturday morning at a mosque in a Minneapolis suburb shattered windows in the imam's office but did not injure anyone, officials said.
At a press conference Saturday afternoon, Potts said investigators are working to determine the cause of the blast. Preliminary findings indicate it came from a destructive device in violation of federal law, he said.
During an afternoon news conference, Richard Thornton, special agent in charge of the FBI's Minneapolis Division, said the explosion was caused by an "improvised explosive device" and investigators had gathered components of the device and were studying how it was assembled. He provided no further details and didn't take questions, citing the ongoing investigation, which is being led by the FBI.
"At this point our focus is to determine ... you know ... who and why," Thornton said. "It was an improvised explosive device that was set off early this morning."
The Department of Homeland Security issued a statement Saturday evening saying that acting DHS Secretary Elaine Duke is aware and the DHS is "in close contact with federal, state and local authorities and local community leaders as the investigation into this matter continues."
The Minnesota chapter of the Council on American-Islamic Relations, or CAIR, was also offering a $10,000 reward.
The Associated Press contributed to this report.