Google has blamed a software bug for erasing emails of some of its Gmail users over the weekend, while making apologies and promising to restore missing emails for every user soon.

A storage software update released by Google introduced the unexpected bug, which caused about 0.02 percent of Gmail users to temporarily lose access to their email, Ben Treynor, a Google vice president, said in a blog post late Monday night.

"When we discovered the problem, we immediately stopped the deployment of the new software and reverted to the old version," Treynor said.

Treynor explained that Google has multiple copies of users' data in multiple data centers, but the rare software bug led to the deletion of some copies of users' emails.

Google also backs up users' information on tapes, which are offline and are protected from the latest software bug, though restoring data from the old-fashioned tapes takes longer than from data centers.

"The good news is that email was never lost and we've restored access for many of those affected. Though it may take longer than we originally expected, we're making good progress and things should be back to normal for everyone soon," Treynor said in the blog post.

Google noted that due to the problem, email sent to some users between 6:00 p.m. PST (Pacific Standard Time) on Feb. 27, and 2:00 p.m. PST on Feb. 28, was likely not delivered to their mailbox, and the senders would have received a notification that their messages weren't delivered.

Latest notice posted Tuesday on a Google website that provides status reports of its Apps services showed that Gmail service disruption was still not completed resolved.

"Google Mail service has already been restored for some users, and we expect a resolution for all users in the near future," the notice said.

"At the moment, we are working on restoring the affected accounts. Once the restore is complete, we will start reinstating accounts and delivering messages," it added.