Amazon says its Web services are back up and running Monday after its facilities on the East Coast went down following a Friday storm in the Washington area.

In a statement to The Washington Post, Amazon Web Services spokeswoman Tera Randall said, that one of the site’s 10 data centers in Virginia lost both primary and backup power, which affected “a single-digit percentage” of site users in the region.

“We began restoring service to most of the impacted customers Friday night, and the remainder were restored on Saturday,” Randall said.

Other Web sites, such as Netflix and Pinterest, were also down after the storm, which whipped up on Friday night and knocked out power for hundreds of thousands of people. As of Monday morning, around 400,000 households were still without power, The Washington Post reported.

This is Amazon’s second big service issue at its Virginia operations in the past month — a power outage in mid-June brought some services down for several hours. In April, the same facility also caused outages for Reddit, HootSuite, Quora and FourSquare.

Amazon has kept quiet on the size of the facility is. Accenture analyst Huan Liu took a crack at estimating the size of Amazon’s total operations and said he believes that the company has a half-million servers altogether and that the US East facility in Virginia is the largest.

The outages may bring up underlying concerns about the Internet cloud services and how the firms that offer cloud service should notify their users about problems.

Several companies experiencing problems put the word out on Twitter. Netflix’s Web site, for example, told users that the site was having problems connecting to the streaming service and then offered tips for connecting on Twitter.

Instagram posted a message on the help section of its site saying that an “electrical storm in Virginia” had hit most of its servers; it was updated later, saying that no data had been lost.

Amazon Web Services has been making a big push in Washington, The Washington Post’s Marjorie Censer reported, trying to capi­tal­ize on the federal government’s push to the cloud and also for big data processing. AWS itself was founded in 2006 and, while the company doesn’t break out AWS profits in its earnings reports, is estimated to have totaled $940 million in sales in 2011.

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