The problem first occurred on Sunday morning. One users known as Wienke said on the Gmail help forum: "This morning when I woke up I only saw two mails in my Gmail box that were sent last night. All mail was gone. I also got some notifications which you will get when you have a new account. Seems something must have been reset".
Further complaints flooded in on the same thread and other threads in the forum.
Google confirmed the bug on its Apps Status Dashboard at 1am GMT this morning.
"This issue affects less than 0.08 percent of the Google Mail user base. This is a revised estimate. Google engineers are working to restore full access. Affected users may be temporarily unable to sign in while we repair their accounts," the search engine said.
In a further update at 3:40am, Google revealed the issue had been resolved for some users, while at 6:36am the search engine said it was "continuing to investigate this issue" and aimed to "provide an update by 8:36am". However, at time of writing Google had yet to issue this update.