Twitter has apologised for the micro-blogging service being unavailable for around two hours on the day before the official opening of the London 2012 Olympics.
Initially, the service said on its network status page: "Users may be experiencing issues accessing Twitter. Our engineers are currently working to resolve the issue."
Later, Twitter said the outage was caused by the coincidental failure of its main datacentre and its back-up systems at the same time.
"I wish I could say that today’s outage could be explained by the Olympics or even a cascading bug. Instead, it was due to this infrastructural double-whammy," Twitter engineering vice-president Mazen Rawashdeh said in a post on the official company blog.
"We are investing aggressively in our systems to avoid this situation in the future," Rawashdeh wrote.
Last month Twitter blamed a "cascading bug" for the outage which also drove frustrated users to other social media sites to complain.
Twitter is expected to be one of the main social networking sites used by sports fans and athletes during the Olympics, with users posing more than 15,000 tweets a second during the Euro 2012 final earlier this month, according to the Guardian.