Facebook says unspecified site issues caused the social-networking site to be slow or unavailable for some of its 500 million users.
Facebook spokeswoman Kathleen Loughlin said in an e-mail to The Associated Press just before 0500 GMT Wednesday that the company was working on the problem. She said in another e-mail at 0525 GMT that the issue was resolved.
Loughlin didn't say when Facebook began acting up, but the phrase "Facebook Isnt Working" was one of the top trending topics late Tuesday on another social-networking site, Twitter.
Facebook also experienced a technical glitch on Sept. 23 that blocked or slowed access for several hours. Tuesday's outage came 12 hours before the company was to make announcements at an invite-only event at its Palo Alto, California, headquarters.