The twitter page of France's Finance and Economy Minister Lagarde is seen in this photo illustration on a computer screen in Paris
The twitter page of France's Finance and Economy Minister Christine Lagarde is seen in this photo illustration on a computer screen in Paris May 30, 2011. The Finance Ministry in Paris confirms that Lagarde's twitter site was launched for her campaign for the vacant post of managing director of the International Monetary Fund (IMF).REUTERS

Millions of Twitter users experienced something they never expected on Thursday as they could not access the microblogging site for over two hours. Speculations were doing the rounds that hackers had attacked the site but a source said that a "cascading bug" in one of its infrastructure components disrupted the network.

The users of the microblogging site witnessed significant down-time and slow service on Thursday morning and it went on for over two hours.

"At approximately 9:00am PDT, we discovered that Twitter was inaccessible for all web users, and mobile clients were not showing new Tweets. We immediately began to investigate the issue and found that there was a cascading bug in one of our infrastructure components," wrote Mazen Rawashdeh, Twitter Vice President of Engineering, on its official blog.

Rawashdeh said that the slowdown in service was caused by hackers, Euro 2012 or GIF avatars as speculated by many.

"This wasn't due to a hack or our new office or Euro 2012 or GIF avatars, as some have speculated today. A "cascading bug" is a bug with an effect that isn't confined to a particular software element, but rather its effect "cascades" into other elements as well. One of the characteristics of such a bug is that it can have a significant impact on all users, worldwide, which was the case today (Thursday)," said Rawashdeh.

"As soon as we discovered it, we took corrective actions, which included rolling back to a previous stable version of Twitter. We began recovery at around 10:10am PDT, dropped again around 10:40am PDT, and then began full recovery at 11:08am PDT. We are currently conducting a comprehensive review to ensure that we can avoid this chain of events in the future," he added.

Twitter offered apology to its users for the inconveniences caused on Thursday.

"It's imperative that we remain available around the world, and today we stumbled. For that we offer our most sincere apologies and hope you'll be able to breathe easier now," said Rawashdeh.

Twitter, which was started in 2006, received criticisms in its early days for frequent outages. However, it worked on improving reliability to cater to its users better.

Twitter is said to have 140 million active monthly users and about 400 million tweets posted daily.