The mysterious disappearance from the Web of one member of a high-profile trio of pro-democracy, pro-America Iraqi bloggers is stirring concern, charges, and counter charges from avid readers of the trio’s site.

The speculation is particularly fevered because Mohammed and Omar Fadhil, two of the three brothers who run IraqtheModel.com, met with President Bush at the White House earlier this month. The third brother, Ali Fadhil, who did not make the trip to America, is the one who has abruptly gone offline.

“This is the last time I write in this blog and I just want to say, goodbye. It’s not an easy thing to do for me, but I know I should do it,” Ali, a 34-year-old Baghdad physician, wrote on the blog early Sunday. “I still love America and feel grateful to all those who helped us get our freedom and are still helping us establishing democracy in our country. But it’s the act of some Americans that made me feel I’m on the wrong side here. I will expose these people in public very soon and I won’t lack the mean to do this, but I won’t do it here as this is not my blog.”

Ali Fadhil’s parting post drew a torrent of messages from those concerned that a voice for democracy in Iraq was being silenced. As of last night, more than 700 comments had been posted to threads discussing his exit.

“Thanks for your courageous stands. I am confused because I have no idea what has happened. I pray for your safety,” wrote one blog reader known as MidwestJim.

“Ali, I have been reading this blog for over a year, it has provided us with a window into Iraq not to be found anywhere else. I appreciate what you have written. Take care of yourself,” wrote another poster, DirtMan.

The Fadhil brothers’ blog has often painted a more optimistic picture of life in Iraq than what has been portrayed in the mainstream press. As a result, the site has become popular with supporters of the American invasion of Iraq and the ongoing effort to organize elections and quell the insurgency

Some left-leaning blogs have speculated that the brothers were in the employ of the American government.

“Are the brothers now or have they ever been in any kind of American pay (beyond the largesse of their rightwing PayPal contributors)?” a Los Angeles based blogger, Joseph Mailander, wrote on his site, MartiniRepublic.com. Mr. Mailander also suggested that the American military may have had a hand in setting up the brothers’ blog.

Mr. Mailander declined to elaborate on his views for this story.

A history professor at the University of Michigan, Juan Cole, used his blog to promote Mr. Mailander’s questions about the brothers. A secretary to Mr. Cole said he was traveling yesterday and unavailable.

Some people using pseudonyms have gone even further, suggesting that the brothers might be working for the CIA.

Many of the Fadhils’ supporters suspect those suggestions may have contributed to Ali’s decision. Ali replied to an e-mail from The New York Sun yesterday but declined to be interviewed. In their Web postings, the brothers have denied receiving support from any foreign government.

The suspicions are fueled, in part, by the unusual entree Mohammed and Omar Fadhil received during their visit to America earlier this month. Their trip was organized by Spirit of America, a California nonprofit organization that supports reconstruction projects in Afghanistan and Iraq.

On December 9, while Mohammed and Omar were in Washington, they received a sudden invitation to come to the White House to meet Mr. Bush, according to Spirit of America’s founder, James Hake.

“It was just a great experience for all of us,” Mr. Hake said. “We spent a half an hour with the president and he was very interested in what they had to say.” Mr. Hake, who accompanied the pair to the White House, said the invitation was arranged by the deputy defense secretary, Paul Wolfowitz.

The pair also attended a Harvard discussion on blogging and met with editors at the Wall Street Journal.

Mr. Hake said he was baffled by Ali’s decision to stop blogging. “It’s as much a mystery to me as anybody at this point,” he said.

In one posting, Ali said his invitation to America was “cancelled” at the last minute. Mr. Hake said yesterday that he thought there was a mutual agreement that it was best for Ali not to come because he is running for election to the Iraqi National Assembly.

“All of us thought because he’s doing that, there could be a perceived conflict and it would be better to not make the trip,” Mr. Hake said. “He may well see that as a disinvitation…. It certainly wasn’t intended as a slap in the face.”

Mr. Hake described as “absurd” the suggestion that the Iraqis are fronts for the CIA. “The CIA stuff would be really funny if it doesn’t actually put them at risk in their country,” he said.

A screenwriter and blogger who had a dinner party for the visiting brothers in Los Angeles last week, Roger L. Simon, said he was “shocked” by Ali’s parting message and the flurry of allegations directed at the brothers.

Mr. Simon accused the Fadhils’ critics of assuming that any Iraqi who supports American forces is a CIA stooge. “There’s one word for that kind of view: racist. That’s saying an Arab can’t think a certain way,” Mr. Simon said.