Storyful's team of journalists, who are based in Asia, Europe and the US, search social media platforms, including Twitter, Reddit, Chinese microblogging service Sina Weibo, Google+ and Pinterest, to source stories and then apply stringent verification tests before tweeting and sharing.
@StoryfulPro was "initially an alert system" for Storyful's clients, founder and chief executive of Storyful Mark Little told Journalism.co.uk. "Increasingly that has moved into a new phase."
Asked whether @StoryfulPro is now competing with @BreakingNews, a Twitter channel launched to provide breaking news, later acquired by NBC News, and which has since expanded by adding @BreakingNewsUK, Little said: "We think of it differently".
"Breaking News does a great job. We don't claim to be the first with the story, but we are always first with the context and those extra details that will make the story stand up or fall down.
"We don't claim to compete with AP or Reuters, we just think breaking news hasn't been addressed properly in the social space."
An example of how @StoryfulPro provides context is illustrated by how it is reporting on the "Prince Harry naked pictures" today. Followers of the account will learn that Storyful is monitoring the story, they then name the news outlets reporting on the story, and retweet Guardian journalist Josh Halliday who explains that "Clarence House aides are warning British press to respect Prince Harry's privacy and not reprint the pictures" (see the @StoryfulPro account).
Announcing the move in a blog post, Little states the "private newswire" is now open to "anyone with a professional interest in extracting news from social noise".
In the post, Little explains the reasoning behind opening the newswire, stating: "Breaking news now emerges in a ‘golden hour’, when skilled intervention is most valuable, when a celebrity death starts to trend on Twitter or an explosive video goes viral on YouTube. In this golden hour, the best journalists are often the ones who stop a story, not start it.
"Storyful was designed to equip news professionals with tools to cope with the uncertainty and opportunity of the golden hour."
Little explains that starting the account as a private newswire allowed Storyful to "trial (and sometimes error) a set of principles" used to verify news stories. He described this to Journalism.co.uk as "a two-year R&D lab".
Storyful also has a closed group on Facebook, which it refers to as its "virtual bureau", and a Google+ page.
Storyful is a newsgathering platform which provides stories to paying news outlets by "acting as a social media 'field producer'". It gives news organisations "early warning of big stories, discovering and verifying content and contacts through a combination of good journalism and pioneering technology".