Twitter has apologised for an outage that left users unable to access the microblogging site for about two hours yesterday.
Twitter went down at about 4.30pm (GMT) and it took about two hours for the fault to be fixed and the site to be fully operational again. It is the second widespread outage to the site in five weeks, and came on the eve of the Olympics.
Mazen Rawashdeh, vice president of engineering at Twitter, said the problem was caused by the dual failure of data centres.
Rawashdeh said in a statement: "The cause of today's outage came from within our data centres.
"Data centres are designed to be redundant: when one system fails (as everything does at one time or another), a parallel system takes over.
"What was noteworthy about today's outage was the coincidental failure of two parallel systems at nearly 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.
"We are investing aggressively in our systems to avoid this situation in the future."
He added: "On behalf of our infrastructure team, we apologise deeply for the interruption you had today."
The outage caused hundreds of people to seek out alternative internet sites on which to post their musings.
One user on Tumblr called cloudsfarbehindme wrote: "omg twitter is down so i can't tweet things that are completely meaningless to the world but i tell them anyways because i have no friends (sic)."
Another wrote: "Twitter... why are you down???? I need my rant space."