US authorities said on Sunday the FBI is seeking suspects after an explosive device tore through part of a mosque in the northern US state of Minnesota as people were preparing for morning prayers.

The blast happened at around 5.00 a.m. on Saturday at the Dar Al-Farooq Islamic Centre in Bloomington in suburban Minneapolis, damaging a room but not causing any injuries, authorities said, Xinhua reported.

One worshipper saw a pickup truck speeding away shortly after the explosion, according to an ABC News report.

The FBI investigators are trying to determine whether the incident was a hate crime and who may have been behind it, said the report.

Mohamed Omar, the centre’s executive director, said the mosque, which primarily serves people from local Somali community, occasionally receives threatening calls and emails.

“If a bias motive is proven, this attack would represent another in a long list of hate incidents targeting Islamic institutions nationwide in recent months,” said Amir Malik, the civil rights director with the Minnesota chapter of the Council on American-Islamic Relations, or CAIR.

The group offered a $10,000 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 US census figures.