It appears the internet forum Reddit has received a demand from the federal government to spy on its users.

Suspicious users drew this conclusion after observing what they perceived as a hint in a transparency statement from Reddit's administrators Thursday.

Reddit is believed to have been issued a 'National security letter,' which is a mass surveillance tool used by federal investigations agencies to seek information about a company's customers or users.

National security letters are almost always accompanied by an open-ended gag order prohibiting firms from acknowledging they've been served.

But while companies can't admit they've received a letter, they can say they've never been served with one, which is what Reddit stated in its previous transparency statement.

However, in the most recent statement released Thursday, the line 'Reddit has never received a National security letter' was missing.

Reddit hinted Thursday that the company might have been served with a 'National security letter' from the feds

The quiet change suggested that Reddit may now be being asked to hand over customer data to FBI investigators under a secretive government authority.

Social media users expressed concern on Twitter and on Reddit itself.

'Is dissent a threat to national security?' tweeted Edward Snowden, a former National Security Agency contractor who leaked classified documents about U.S. surveillance programs to the media and is now exiled in Moscow.

'When you ask someone 'Are you helping authorities in investigations?' and they say 'I'm not allowed to discuss that with you,' I think the question has been answered,' wrote Reddit user khegiobridge.

Edward Snowden, left, leaked classified documents about U.S. surveillance programs, specifically regarding his previous employer, the National Security Agency, to the media and is now exiled in Moscow

'I've been advised not to say anything one way or the other,' Reddit Chief Executive Officer Steve Huffman, who goes by 'spez' on the site, said in a thread discussing the change.

'Even with the canaries, we're treading a fine line,' Huffman said, referring to hints known as 'warrant canaries.'

Reddit did not respond to a request for comment. The Federal Bureau of Investigation did not respond to a request for comment.

National security letters have been available as a law enforcement tool since the 1970s, but their frequency and breadth expanded dramatically under the USA Patriot Act, which was passed shortly after the September 11, 2001 attacks on the United States by Islamist militants.