Tenants of the Fisher Plaza data center carry servers out of the building Friday morning. The building houses the Bing Travel servers, among others.

A fire at downtown Seattle's Fisher Plaza has interrupted service at some top Web sites, including Microsoft's Bing Travel and Authorize.net.

It's a little unclear exactly when the fire at the Fisher Plaza data center started--some reports say Thursday night, others say just after midnight Friday. A message on Bing Travel pins the problems on a blown transformer.

"The blown transformer knocked out power to the entire building, which is home to the Bing Travel servers," a message on the site says. "This is isolated to Bing Travel only, and there is no impact to any other aspect of Bing."

Bing Travel says it's working hard to restore service, and has set 5 p.m. PDT Friday as the target time for resumption of service. "In the meantime, you may use Microsoft travel partner Orbitz for your travel needs," the site says.