By Kiran Khalid, CNN

The Muslim community in Des Moines, Iowa, is as small as it is diverse. The members of the four mosques here are from Yemen, Somalia, Pakistan and Bangladesh, among other nations. Although the roots of the Muslims here may be worlds apart, the community is a tight-knit group. That’s why what happened at their mosques here is alarming to so many of its members.

“That was really surprising, very sad that somebody would come or the FBI or Homeland Security would send somebody here to pretend to be Muslim and try to find out what goes on here. I feel there is no need for that,” said Dr. Hamed Baig, president of the Islamic Center of Des Moines.

Baig is talking about 42 year-old Arvinder Singh. Baid says he saw Singh a couple of times at his mosque, and that Singh would have been welcomed like all newcomers interested in learning about Islam. But it wasn’t until recently that members of the community discovered that Singh, who was raised a Sikh, was allegedly sent into their mosques to spy for the FBI.

Singh told CNN that the FBI told him, "'You look Middle Eastern, and we need your help for the war against terror.'"

Singh says he obliged because he had been charged with “selling or transferring precursor substances for an unlawful purpose” back in March of 2002. Singh says he unwittingly sold more than the legal limit of Sudafed, often used in meth labs to create the illegal drug crystal meth. The charge was deferred but the Indian-born immigrant says he worried about getting his citizenship, something he desperately wanted. Singh says the FBI came to him with a simple tradeoff: We’ll help you get your citizenship if you help us get some terrorists.

Singh spoke to CNN in an exclusive on-camera interview from Hardin County Jail in Iowa, where he’s been awaiting deportation. He says the promise to expunge his record of that felony was another promise left unfulfilled by the FBI: When he tried to apply for citizenship, he was arrested.

Singh says when he was first approached by agents, “I was surprised. I said, ‘Me? I have no idea about this’ And they said ‘We’ll train you. You’ll get used to it. We’ll make you go and do some work for us.’”

Singh says he assumed a Muslim identity– Rafik Alvi - and went into the mosques pretending to be interested in converting. He says he frequented mosques all over the state but attended the four in Des Moines regularly for seven years. He says sometimes the FBI gave him pictures of persons of interest and he would confirm that they were at the mosque. On a few occasions, Singh says he taped his conversations with congregants.

“They wanted me to go investigate some people in the area,” Singh told CNN in a jailhouse interview. “See what they’re doing, who they’re meeting. Who’s their family member, who’s attending them, what they are talking about. That kind of work.”

Anis Rehman, executive board treasurer of the Islamic Center of Des Moines and a college professor says he feels violated. “To know that somebody made an intrusive entry into the masjid for purpose other than prayer, or other than socializing or taking care of anybody who is in need makes me very much nervous and embarrassed, too, that I belong to a community where we have a member who has come for some other purpose. But later when we saw that he was not actually a member but a pretender then it made me more angry,” Rehman said.

Basim Bakri says he knew Arvinder Singh who used an American name, “Roger.” He says if Singh’s claims are true, the FBI just took a step backwards in building trust with the Muslims in his community.

“I think the FBI owe[s] us an apology because they did violate our civil rights,” Bakri said.

Rehman says the idea of a FBI informant in their tiny mosque is not only offensive but baffling. “I find that to send an impostor into our community which is so small where not only we know each other but (where) the law enforcement agents can perhaps pick each one of us by name and by family, I don’t think that the incident [on] 9/11 could warrant such action in a small community like ours.”

Weysan Dun, the FBI’s special agent in charge of the Omaha Division says the agency doesn’t confirm or deny the identity of its informants nor do they cut deals like the one Singh described. But he adds that if such surveillance were to occur, it would be unrealistic to involve mosque leaders.

“We approach our investigations with the intent of finding the truth and we are just as eager to prove someone innocent as we are to prove guilt. If we involve mosque leaders prior to conducting surveillance on a member of their community, we could be tarnishing the reputation of the subject of the investigation if it turns out the person was innocent. Thus, to protect those against whom unfounded or malicious accusations have been made, we cannot involve others prior conducting investigative activities,” Dun said in an email to CNN.

But that comes as little consolation to the American Muslims such as Bakri who says he’s demoralized that the partnership his community believed it had built with law enforcement was a one-way street.

“It wasn’t right at all, it wasn’t right from the beginning and they have no right to do that,” Bakri said, shaking his head in dismay.