NEW YORK (AP) — Facebook went down for almost a full day across parts of North America and Europe, but it’s still not saying exactly what happened.

All the social network said Thursday was that the outages, which affected users and advertisers worldwide, resulted from a “server configuration change.” It offered no further details.

Facebook and its apps — Instagram, Facebook Messenger and WhatsApp — started experiencing problems midday Wednesday on the U.S. East Coast. Facebook was still having sporadic issues Thursday morning.

Facebook did not say how many users were affected or why the outage took so long to fix. In a tweet about 24 hours after the problems began, Facebook apologized and thanked people for their patience. It didn’t elaborate on the server change.

The outage is yet another publicity problem for a company already dealing with privacy issues and regulatory probes .

The disruption isn’t likely to hurt advertisers much, since they usually pay for ads per click or impression.