TORONTO -- The Sun News Network went off the air at 5 a.m. ET Friday after negotiations to sell the troubled television channel were unsuccessful.

No on-air announcement was made as the screen went dark and was replaced moments later with the Sun TV logo.

The closure of the conservative-angled news channel follows months of uncertainty surrounding its fate, after Postmedia Network Canada Corp. announced plans to purchase the Sun Media newspapers and websites from Quebecor for $316 million.

The Sun News channel was not included in the deal, which sparked outsiders to suggest the network could fold after years of struggling in the ratings.

In a news release to coincide with the early morning shutdown, Sun Media Corp. said it spent months actively seeking a potential buyer.

But it said "no party capable of taking over the channel was found" and that in view of the financial losses "there was no alternative to closing Sun News."

"This is an unfortunate outcome; shutting down Sun News was certainly not our goal," said Julie Tremblay, president and CEO of Media Group and Sun Media Corporation.

"Over the past four years, we tried everything we could to achieve sufficient market penetration to generate the profits needed to operate a national news channel. Sadly, the numerous obstacles to carriage that we encountered spelled the end of this venture."

Adding further questions about the future of the network was an short-term agreement with Postmedia which allowed Sun News to licence the rights for its existing logo for only a year before Postmedia required the broadcaster to distance itself from the brand.

"The closure is regrettable for the Canadian broadcasting system, which is losing a distinctively Canadian voice in the national news space," said Tremblay.

"We thank all employees for their daily efforts and the talent they have contributed to the channel. We wish them all the best in their future endeavours."

Sun News Network hit the airwaves in April 2011 with heightened expectations and the watchful eyes of media observers who nicknamed it "Fox News North."

The channel promised to balance the "lefty bias" of traditional Canadian media, but its operations were plagued by tight production budgets which often left it with limited on-the-ground reporting and a large portion of its airtime dedicated to commentary and heavily editorialized news coverage.

But it also quickly drew controversy with its occasionally combative on-air approach.

One of the most famous examples happened when former "Canada Live" host Krista Erickson drilled Quebec-born dancer Margie Gillis about whether she could receive government money for her dance performances. The segment went viral and drew a record number of complaints from viewers who felt Erickson was being unfair, but the Canadian Broadcast Standards Council eventually ruled the "aggressive" interview was acceptable.

Last September, Sun Media's outspoken right-wing host Ezra Levant faced the ire of the Liberal party when he criticized Justin Trudeau for kissing a Toronto-area bride in a wedding photo. The bride later said Trudeau secured the groom's OK beforehand.

Levant's commentary also slurred Trudeau's mother, Margaret, and his late father, former prime minister Pierre Trudeau. Sun News issued an apology after Trudeau said he would no longer speak to the outlet's reporters until there was an appropriate response.

The channel also got behind "Ford Nation," a commentary series hosted by Rob and Doug Ford, that was pulled from the schedule less than a day after it premiered.

Despite plenty of media attention, Sun News was never able to translate the spotlight into a ratings boon.

Executives at the channel argued that at least part of that reason was the country's broadcast regulator decided against allowing Sun News to be carried on basic cable.

In 2013, the Canadian Radio-television and Telecommunications Commission said Sun News didn't meet the criteria for mandatory carriage.

Sun News responded by saying the decision would spell the end of the channel.

Losses had mounted at the network, according to CRTC documents which said it lost $17 million in 2012 and $14.8 million in 2013.

Last December, a report in the Globe and Mail quoted a source "familiar with the negotiations" who said that Moses Znaimer's ZoomerMedia Ltd. was negotiating to acquire the network.

However, an official bid for the channel never surfaced.

ZoomerMedia operates print, TV, radio, digital, consumer shows, and conferences aimed at the over-45 demographic, and Znaimer is known as one of the creators of the Citytv brand.

Minutes after the station went dark, an on-screen message from Rogers Cable read: "Sun News Network is no longer available, at the discretion of the programmer."

Statement from Sun Media Corporation, February 13, 2015 05:00 ET

After attempting to establish Sun News as a viable news channel in the Canadian broadcasting landscape and encountering a series of barriers to carriage, Sun Media Corporation regrets to announce today that it is closing the station. At the time of this release, Sun News Network is already off the air.

"This is an unfortunate outcome; shutting down Sun News was certainly not our goal," said Julie Tremblay, President and CEO of Media Group and Sun Media Corporation. "Over the past four years, we tried everything we could to achieve sufficient market penetration to generate the profits needed to operate a national news channel. Sadly, the numerous obstacles to carriage that we encountered spelled the end of this venture."

Sun Media Corporation spent months actively seeking a potential buyer but no party capable of taking over the channel was found. Therefore, in view of the financial losses, there was no alternative to closing Sun News.

"The closure is regrettable for the Canadian broadcasting system, which is losing a distinctively Canadian voice in the national news space, and also, most importantly, for all the Sun News employees who are losing their jobs. We thank all employees for their daily efforts and the talent they have contributed to the channel. We wish them all the best in their future endeavours," concluded Julie Tremblay.