A fire on Friday at an Amazon.com Inc data center under construction in Virginia was quickly extinguished and all workers at the site left safely, the company and county officials said.

The data center was in the early phases of construction by a third-party contractor when roofing materials ignited.

"It was a fire on the roof, involving the roof, roofing materials and construction materials. Workers who were on the roof when the fire broke out were able to extricate themselves safely," said Mary Maguire, a Loudoun County Fire, Rescue and Emergency Management spokeswoman.

"The call came in at about 10:12 a.m.," said Maguire.