Al-Farooq Youth & Family Center (credit: Dar Al-Farooq Center)

WASHINGTON, Aug. 7 (Xinhua) -- No one was hurt in the mosque blast in northern U.S. state of Minnesota at the weekend, but anxiety is accumulating in fear of more hate crimes against Muslims may occur across the country.

The blast happened as worshippers prepared for morning prayers at around 5 a.m. Saturday at the Dar Al-Farooq Islamic Center in Bloomington in suburban Minneapolis, shattering windows, damaging a room but not causing any injuries, authorities said.

The FBI, still trying to determine whether the incident was a hate crime, said on Sunday that the suspects used an "improvised explosive device."

"It's so scary," Mohamed Omar, the center's executive director, lamented.

"We feel like it's much deeper and scarier than like something random," he was quoted by a CBS news report on Monday.

"It hurts me to know this is how we treat our neighbors, how we treat our fellow Minnesotans," a woman told the CBS Minnesota station.

Minnesota Governor Mark Dayton visited the mosque on Sunday, describing the bombing as "so wretched" and "not Minnesota."

"This is an act of terrorism. This is against the law in America," the governor said at a news conference afterwards.

The group offered a 10,000-dollar reward for information that leads to an arrest or conviction.

Minnesota hosts the largest Somali community in the United States, roughly 57,000 people, according to the latest U.S. census figures.