Users of Google's email service Gmail were unable to access their accounts tonight.
People a round the world reported being presented with an error message as they tried to log in to their accounts.
A message on Google.com stated: " We're investigating reports of an issue with Gmail. We will provide more information shortly."
The topic was soon trending on Twitter, where users later reported that the service had returned to normal.
Google later added on its website: "The problem with Gmail should be resolved.
"We apologise for the inconvenience and thank you for your patience and continued support.
"Please rest assured that system reliability is a top priority at Google, and we are making continuous improvements to make our systems better."