UPDATE: Twitter began coming back online for many around 6:15 p.m.
Twitter went down on Wednesday evening around 5 p.m.
A status report from Down Right Now confirmed a "likely service disruption" Wednesday evening.
Facebook users have taken to the social network to report the downtime, according to a search of public Facebook posts on Openbook.
However, this outage may not be affecting all users. At almost 6 p.m., DownForEveryoneOrJustMe.com reported that Twitter.com was still up, though feeds on Twitter and clients such as Tweet Deck were unresponsive at that time.
Just before 6 p.m., an update from the Twitter API feed, obtained via Down Right Now, addressed the outage and listed a possible cause: "If you can't access Twitter or @twitterapi right now, it might be due to a rather large internet outage."
Have you had problems with Twitter? Let us know in the comments.