A web hosting company has said it shut down a blogging platform that was home to over 70,000 bloggers because a "link to terrorist material" and an al-Qaeda "hit list" was posted to the site.
BurstNet said Blogetery.com also posted "bomb-making instructions".
The company said it acted after receiving "a notice of a critical nature from law enforcement officials".
But the move has angered bloggers who use the platform and say they were given no notice of the shutdown.
In response Blogetery.com said its server had been "terminated without any notification or explanation."
The site added that it is trying to resolve the situation.
BurstNet defended its position.
"The posted material, in addition to potentially inciting dangerous activities, specifically violated the BurstNet acceptable use policy" said the web host firm.
BurstNet also claimed that the site had a history of previous abuse.
The news blog Cnet.com reported that officials from the Federal Bureau of Investigation (FBI) told BurstNet on 9 July that al-Qaeda materials had been found on Blogetery's servers.
It also claimed that material allegedly found on the server included "the names of American citizens targeted for assassination by al-Qaeda" as well as messages from Osama bin Laden and other leaders of the terrorist organisation.
BurstNet's chief technology officer, Joe Marr, said that the FBI sent a "Voluntary Emergency Disclosure of Information" request to the firm.
Sources have confirmed to the BBC that this was the case but FBI spokesman Paul Bresson said the bureau does not comment on active investigations.
However he did say that the FBI had not asked for any websites to be shut down.
The FBI does not have the power to remove content from websites or to take them down. That can only be done with the authority of a judge.
Calls to BurstNet were not returned.
For days bloggers have speculated as to the cause of the shut down at Blogetery.com.
Theories ranged from the FBI using the Patriot Act to silence bloggers to a belief that perhaps child pornography had been found on one of the blogs.
On one forum, a number of users were upset about not getting any advance warning to back up information they had stored on the server.
One frustrated user wrote "so BurstNet can "kill" your server and give you BS reasons about some "law enforcement officials".
"Who needs a hosting service that does not fight for their clients?" wrote another.
The Centre for Democracy and Technology has also expressed concern about what happens to the 70,000 plus bloggers who have had their blogs terminated
"As a free speech advocate, I certainly think it is unfortunate that what I assume are many thousands of perfectly innocent blogs were taken down here," John Morris, the head of the Centre for Democracy & Technology's free expression project told BBC News.
"I hope our society is able to figure out a way to address one bad apple in a pool of content without collateral consequences for the innocent speakers. This (case) highlights the fragility of speech on the internet when thousands of speakers have their speech removed."
Adding to the mystery is the news that another online service that helped users create web message boards was taken offline a week after Blogetery.com.
While there has been no official link between the two cases, iPBFree.com said they are "gone for good" and had "absolutely no warning" and that the reasons are "tied up in legalities".
On a temporary forum called the unofficial iPBFree refuge a statement said "the main site, all the thousands of forums, and the iBPFree Facebook and Twitter pages are gone."
While the site has been unable to reveal why it has gone dark, users have been equally frustrated as those at Blogetery.com about at the potential loss of material.
One wrote "I'm personally devastated. My forum was a blogging forum and many of my members used it to keep a record of what they do from day to day. May not sound like much, but it was very important to them and me."
Another suggested that while the shut down poses more questions than answers "one thing about the internet is that nothing is really kept hidden away forever".