San Francisco  - Google on Tuesday apologized for an outage that struck possibly millions of users of its email system, Gmail, earlier in the day.

"The Gmail outage that affected many consumers and Google Apps users worldwide is now over. Users should find that they're able to access their email now without any further problems," said Acacio Cruz, Gmail site reliability manager, in a blog posting.

"The outage itself lasted approximately two and a half hours from 0930 GMT. We know that for many of you this disrupted your working day. We're really sorry about this ... our engineers are still investigating the root cause of the problem," Cruz said.

Google did not say how many clients were affected by the incident, but reports of trouble flooded the internet from all over the world.

Google stressed that problems with Gmail were very rare, but the incident was seen as a major embarrassment for the company, which is trying to persuade computer users to store more of their data online. (dpa)