Authorities said they allowed the plot to proceed to obtain evidence to charge the suspect with attempted use of a weapon of mass destruction.
Mr. Jamal said there is concern in the Somali community that Mr. Mohamud was “lured into an illegal act.”
“Rest assured that the community is very against anyone who tries to do harm to the citizens of this country,” he said. But many Somalis in the United States are wondering whether Mr. Mohammud’s rights were violated by federal agents, he said.
Why “did they tell him to go along with this heinous crime?” Mr. Jamal said.
The FBI affidavit said that it was Mr. Mohamud who picked the target of the bomb plot, that he was warned several times about the seriousness of his plan, that women and children could die, and that he could back out.
Officials said Mr. Mohamud had no formal ties to foreign terror groups, although he had reached out to suspected terrorists in Pakistan.
Agents had some face-to-face meetings with Mr. Mohamud. On Nov. 4, in the back country along Oregon’s coast, they persuaded him that he was testing an explosive device — although the explosion was controlled by agents.
On Friday, an agent and Mr. Mohamud drove into downtown Portland in a white van that carried six 55-gallon drums with detonation cords and plastic caps, but all of them were inert.
Mozafar Wanly, father of the imam at the Salman Al-Farisi Islamic Center in Corvallis, said the fact that Mr. Mohamud was e-mailing someone in Pakistan shows nobody in the United States supported his extremist ideology.
“He’s reaching for people outside because he doesn’t find any terrorists here,” he said.
The fire at the center 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 Mr. Mohamud sometimes worshipped there.
Arthur Balizan, special agent in charge of the FBI in Oregon, said there’s no conclusive link between the fire and the bombing in Portland or specific evidence that the fire was a hate crime, other than the timing.
No one was injured 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 younger Mr. Wanly, the center’s imam.