The Google+ social networking site malfunctioned this weekend, spamming its users with repeated notifications via email.
Google+, which is being beta tested with a limited number of users, ran out of disk space on Saturday, causing the glitch, said Vic Gundotra, a Google senior vice president of engineering.
"Please accept our apologies for the spam we caused this afternoon. For about 80 minutes we ran out of disk space on the service that keeps track of notifications," he said.
"Hence our system continued to try sending notifications. Over, and over again. Yikes," he wrote in a Google+ post.
"We didn't expect to hit these high thresholds so quickly, but we should have. Thank you for helping us during this field trial, and once again, we are very sorry for the spam," he added.
Google+ is the company's latest and most high-profile attempt to date to launch a social networking service that competes with Facebook, after a number of failed attempts throughout the years.
With Google+, the company is betting on the site's mechanism for sharing content, which Google maintains is more intuitive thanks to privacy controls that Google believes are easier to use than Facebook's.
Privacy experts have given Google early kudos for launching Google+ to a limited number of testers, which gives the company a chance to stamp out critical bugs, including privacy glitches, before opening up the service massively worldwide.