Remove existing Facebook account from OS X

I had synchronized my personal Facebook account on OS X Mountain Lion in System Preferences > Mail, Contacts & Calendars through the Facebook tab. I removed it and synchronized my official account on it, but I'm still getting notifications for the personal account.

How do I remove the personal account details permanently and stop the notifications?

Update

I have upgraded my Mac to OS X Mavericks 10.9, but the problem exists on the upgraded OS X version too.

Edit

I have found another thing with my mac. This issue happens only for my official account. If i have synchronized any other accounts. It doesn't happen. Working fine. What may be the problem with this?

My suggestion would be to log out of the current Facebook account. Then go into your user's Library folder (holding down the alt / opt key while in the "Go" menu in Finder and you will see a new entry "Library"). In your Library folder enter the subfolder "Preferences" and delete these two files:

com.apple.accountsd.plist & com.apple.internetaccounts.plist (or just shove them over to the Desktop for testing)

Log out and back into the correct account and see if there are any notifications in Notification Center still listed. If yes, then download Onyx from http://www.titanium.free.fr/downloadonyx.php and let it do an automation where it clears all caches. When Onyx is done it will ask you to restart.

From here you should be good and there should be no trace of the original/old Facebook account. If however you notice anything still being left over, comment back with more information.