SAN FRANCISCO (AP) -- Facebook says some users were briefly unable to access the site because of a technical glitch.

The social networking site with over 1 billion users worldwide says on Monday it made a change to its domain name system setup.

The change resulted in some users temporarily not being able to reach the site.

The problem was detected and the site is now fully back.

A DNS acts like a phone book for the Internet, translating a domain name like facebook.com into a number that points to a specific host computer.

Facebook did not say how many users were affected or for how long. Some technology blogs say the problems lasted about 20 minutes.