Some European Amazon Web Services (AWS) customers could face up to two days of disruption after a lightning strike in Dublin took down some of the firm's servers.
AWS said that the power failure on Sunday was limited to just one Availability Zone, which generally corresponds to one datacentre.
AWS launched the multiple Availability Zones feature in 2008, allowing customers to run applications across multiple datacentres so that they are less likely to be affected by one failing generator.
The company has advised customers to log-in to the AWS Console to see whether their account has been affected by the outage.
An Amazon service status update said that the lightning hit a transformer owned by a utility provider that generates power for the Availability Zone, sparking an explosion and fire.
Electrical load would normally be picked up by backup generators, but these were also disabled by the explosion. AWS said that it had to manually bring the generators back online to get the Availability Zone running again.
The last status update explained that many Elastic Compute Cloud volumes will be restored shortly, but that this could take 24 to 48 hours to complete.
"Because of this, in some cases we will provide customers with a recovery snapshot instead of restoring their volume so they can validate the health of their volumes before returning them to service," said the firm.
Customers of Microsoft's EMEA Business Productivity Online Services were also affected by the outage, although Microsoft said in a Twitter post on Monday that the service has now been restored.
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NatWest outage comes a day after Barclays' IT systems shut out customers and staff