What we know about the Minnesota mosque explosion Officials say a "destructive device" caused the explosion.

 -- Federal authorities are investigating an explosion at a Minnesota mosque this weekend that the governor deemed an "act of terrorism."

Officials say a "destructive device" in violation of federal law caused the blast Saturday in Bloomington, about 10 miles outside of Minneapolis.

Here's what we know about the investigation:

The blast

At 5:05 a.m. Saturday, Bloomington police responded to an explosion at the Dar Al Farooq Islamic Center, authorities said.

The blast shattered windows in the imam’s office, but no one was hurt, officials said.

About a dozen people were in a nearby room for morning prayers at the time, according to The Star Tribune.

The explosion woke many residents of the neighborhood, The Tribune reported.

The investigation

The investigation was turned over to federal officials, and the FBI said the preliminary investigation indicates the explosion was caused by a destructive device in violation of federal law.

Richard Thornton, special agent in charge of the FBI's Minneapolis Division, said this weekend the explosion was caused by an "improvised explosive device" and investigators had gathered components of the device and were studying how it was assembled.

"At this point our focus is to determine ... who and why," Thornton said.

Federal officials said investigators are following leads as they search for suspects.

The Department of Homeland Security said in a statement Saturday that it "fully supports the rights of all to freely and safely worship the faith of their choosing and we vigorously condemn such attacks on any religious institution. We are thankful that there were no injuries, but that does not diminish the serious nature of this act."

The DHS added, "We are in close contact with federal, state and local authorities and local community leaders as the investigation into this matter continues."

The governor and the Muslim community react

Minnesota Gov. Mark Dayton called the blast an "act of terrorism," The Tribune reported.

"The destruction done to this sacred site is just unthinkable, unforgivable," Dayton said, according to newspaper. "I hope and pray the perpetrator will be caught and prosecuted to the full extent of the law."

Officials with the Muslim American Society condemned the attack and said all indications point to a hate crime.

Officials said most of the imam's office was destroyed and that mosque members are saddened and shocked.

"We feel like it's much deeper and scarier than like something random. ... It's so scary," Mohamed Omar, executive director of the Dar Al-Farooq Islamic Center, said, according The Associated Press.

The Council on American-Islamic Relations (CAIR) said it is urging mosques and Islamic centers nationwide to step up security measures.

CAIR and the Muslim American Society are offering rewards for information leading to an arrest.