Reddit has removed a notice, known as a warrant canary, from its transparency report for 2015, suggesting that it may have received a secret national security order for user data.

The removal of the warrant canary is a reminder to users that their online communications could be the target of investigators.

The most controversial of the orders is the National Security Letter, which gives the government the authority to compel the production of customer records held by telephone companies, Internet service providers and other electronic communications service providers.

Companies that have been asked for user data by the government are usually served the requests under a “gag order” that prohibits them from disclosing the request for data.

These companies can’t say they have received the NSL requests when they do, but they do inform users when they don’t get such orders through the warrant canary device. Akin to the bird in the coal mine, the warrant canary also dies if there is trouble in the form of a secret order for user information.

The removal of the warrant canary notice could hence suggest that Reddit is trying to communicate to its users that it has received a secret security order for user data after Jan. 29, 2015.

In its 2014 transparency report, the online message board had included the canary, when it wrote that “as of January 29, 2015, reddit has never received a National Security Letter, an order under the Foreign Intelligence Surveillance Act, or any other classified request for user information.” If it ever received such a request, it would seek to let the public know it existed, it added.

Reddit and other tech companies have in the past demanded that they should be able to inform their users about NSLs. Twitter filed a suit in court in 2014 against the Department of Justice after the agency denied the company permission to publish a transparency report in which Twitter wanted to provide aggregate numbers of national security process in smaller bands than those permitted by the government. Reddit also joined a friend-of-the-court brief in support of Twitter.

In response to a user's questions about why the national security canary found in the 2014 transparency report is no longer present in the 2015 report, Reddit CEO Steve Huffman (who goes by the handle “spez” on the site) said he had “been advised not to say anything one way or the other." Even with the canaries, Reddit is treading a fine line, he added.