SAN JOSE (CBS SF/CNN) — A massive outage swept over Google’s services including YouTube, Gmail and Google Classroom early Monday, knocking them offline for about an hour.

Since the outage took place in the early morning hours and services were restored by 5 a.m. PST, San Francisco Bay Area residents likely never noticed.

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“Today, at 3:47 a.m. PT Google experienced an authentication system outage for approximately 45 minutes due to an internal storage quota issue,” the company said in a statement. “Services requiring users to log in experienced high error rates during this period. The authentication system issue was resolved at 4:32 a.m. PT. All services are now restored. We apologise to everyone affected, and we will conduct a thorough follow up review to ensure this problem cannot recur in the future.”

However, the company did warn that for some users their Gmail remained impacted.

“We’re investigating reports of an issue with Gmail,” Google said in a statement. “The affected users are able to access Gmail, but are seeing error messages, high latency, and/or other unexpected behavior.”

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For the rest of its apps, Google said it will work toward restoring service for the remaining people who are still unable to access, but the problems should largely be resolved.

“Please rest assured that system reliability is a top priority at Google, and we are making continuous improvements to make our systems better,” the company said.

Downdetector, a service that registers complaints about unavailable internet services, showed tens of thousands of people had been unable to use Google and its apps.

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Internet services fail from time to time for a variety of reasons: server errors, incorrectly installed maintenance routines or a host of other potential goofs and glitches. Google’s most recent major outage took place in September, when Google Docs went down for several hours.