Google reporting “Service disruption”. Related to OAuth outage?

The status page at https://status.cloud.google.com/ has now been updated to include

"We are investigating an issue with Authentication services. We will provide more information by 07:30 US/Pacific."

Here is a direct link to the specific incident: https://status.cloud.google.com/incident/appengine/16003

Able to log in to our services now; waiting to hear what the root cause is at 7:30a, though. This post-mortem is going to be a doozy!