Someone set fire to an Islamic center on Sunday, two days after a man who worshipped there was accused of trying to blow up a van full of explosives during Portland's Christmas tree lighting ceremony. Other Muslims fear it could be the first volley of misplaced retribution.

CORVALLIS — Someone set fire to an Islamic center on Sunday, two days after a man who worshipped there was accused of trying to blow up a van full of explosives during Portland's Christmas tree lighting ceremony. Other Muslims fear it could be the first volley of misplaced retribution.

The charges against Mohamed Osman Mohamud, a Somali-born 19-year-old who was caught in a federal sting operation, are testing tolerance in a state that has been largely accepting of Muslims. Muslims who know the suspect say they are shocked by the allegations against him and that he had given them no hint of falling into radicalism.

The fire at the Salman Al-Farisi Islamic Center in Corvallis was reported at 2:15 a.m., and evidence at the scene led authorities to believe it was set intentionally, said Carla Pusateri, a fire prevention officer for the Corvallis Fire Department.

Authorities don't know who started the blaze or why, but they believe the center was targeted because Mohamud occasionally worshipped there.

Arthur Balizan, special agent in charge of the FBI in Oregon, said there's no conclusive link to the bombing in Portland or specific evidence that it's a hate crime, other than the timing.

U.S. Attorney Dwight Holton vowed to prosecute the case aggressively.

"The fact is that violent extremists come from all religions and no religion at all. For one person to blame a group, if that's what happened here, is uniquely anti-American and will be pursued with the full force of the Justice Department," he said.

Mohamud was being held on charges of plotting to carry out a terror attack Friday on a crowd of thousands at Portland's Pioneer Courthouse Square. He is scheduled to appear in court today.

On Friday, he parked what he thought was a bomb-laden van near the ceremony and then went to a nearby train station, where he dialed a cell phone that he believed would detonate the vehicle, federal authorities said. Instead, federal authorities moved in and arrested him. No one was hurt.

There were also no injuries in Sunday's fire, which burned 80 percent of the center's office but did not spread to worship areas or any other rooms, said Yosof Wanly, the center's imam.

After daybreak, members gathered at the center. "I've prayed for my family and friends because obviously if someone was deliberate enough to do this, what's to stop them from coming to our homes and our schools?" said Mohamed Alyagouri, a 31-year-old father of two who worships at the center.

Wanly said he was thinking about temporarily relocating his family because of the possibility of hate crimes.

"We know how it is, we know some people due to ignorance are going to perceive of these things and hold most Muslims accountable," Wanly said.

In Portland, residents are alarmed by the terror plot, but Mayor Sam Adams said they are "not going to let this change our values of being an open and embracing city." He said he beefed up patrols around mosques "and other facilities that might be vulnerable to knuckle-headed retribution" after hearing of the bomb plot.

The FBI was working closely with leadership at the Corvallis center as agents investigated the fire, Balizan said. A $10,000 reward was offered for information leading to an arrest.