Facebook and its photo-sharing application Instagram, as well as private messaging service Messenger, crashed for mostly European users at around 5 a.m. EST (10:00 GMT), Downdetector said.
The number of complaints about problems with Facebook and Instagram was in the hundreds, while Messenger recorded more than 2,000 reports, far above its baseline of 1.
A Facebook spokesperson told the Daily Mail they were aware of people having trouble sending messages on social media sites and were working to "get things back to normal" as quickly as possible.