Instead of the usual feed of tweets, visitors to the Twitter homepage are now met with a blue screen and the message, "Something is technically wrong. Thanks for noticing—we're going to fix it up and have things back to normal soon."
As of Thursday afternoon, there were close to 50,000 reports of problems with the website, according to downdetector.com.
Most of the United States, and areas of South America, Europe and Asia appear to be affected, according to downdetector.com's outage map.
DigitalAttackMap.com reports a large-scale internet outage occurring in the U.S.
Twitter says on its status page the service disruption began just before 3 p.m. EDT, and that it's "investigating issues."
It's unclear what caused the outage or when it will be fixed.
Twitter experienced its biggest-ever outage in March, which impacted millions of users worldwide, KPIX-TV reported. Twitter said that outage was caused by a "server configuration change."
This is a breaking news story. Check back for updates.