Twitter suffered an outage for several hours on Thursday.
The social networking site has yet to give a formal reason for the outage.
"Users may currently be experiencing issues accessing Twitter," a Twitter spokesperson told V3.
"We're aware of the issue and are looking into it."
The site-wide outage occurred around 8:30 AM PST when Twitter acknowledged a service disruption on its status page. The site had been down for some hours before service was reestablished for its users.
The disruption is Twitter's second outage in as many months. The microblogging site had a similar outage in late June which had initially been claimed by a group of hackers as a denial of service attack, but those claims were later discredited.
Twitter blamed that disruption on a cascade bug in its infrastructure. a software issue that "cascades" across other parts of the infrastructure to cause service delays and outages.
Twitter's outage comes the same day as the large scale outage of Google Talk. Google saw a global distribution of its Talk service early Thursday. The service outage started around midday UK time and wasn't fixed until the late afternoon.
Google has apologised for the disruption but has yet to comment on what may have caused the failure.
UPDATE: Twiitter has released a blog post explaining why the outage occurred. The microblogging site has blamed the service disruption on two parallel systems in its datacentre failing.
"The cause of today's outage came from within our datacentres. Datacentres 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," said Twitter vice president of engineering Mazen Rawashdeh.
"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."
Twitter apologised to users and said it is working to improve the site's infrastructure.
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