SAN FRANCISCO (CBS SF) -- A Facebook outage Thursday morning shut down millions of users around the world.

No word yet as to the cause of the outage, which was first reported around 9:20 a.m. PT.

The outage was reported by Twitter users around the world using the hashtag #facebookdown.

Is this the end of Social Media? #facebookdown https://t.co/xHGH1JH4hp

— BHW Group (@BHWGroup) September 24, 2015

//platform.twitter.com/widgets.js

#facebookdown in mezzo mondo sembra, a vedere i tweet che arrivano. Ecco la mia schermata pic.twitter.com/X2QdtBkFiq

— Francesco Marinari (@framar1977) September 24, 2015

//platform.twitter.com/widgets.js

The revolution will not be Facebooked. #facebookdown pic.twitter.com/yn6sWuB4J0

— cortez wright (@cortezjwright) September 24, 2015

//platform.twitter.com/widgets.js

By 10:00 a.m., it appeared most users were back online. No word on what caused the outage.