Facebook has decided to double the size of its planned data center in Oregon before the first part of the project is even built, the latest sign of the company’s rapid growth.

Facebook said in January that it was building its first wholly owned data center in Prineville, Oregon, a 147,000-square-foot facility that’s due for completion early next year. It’s now decided to add another 160,000 square feet of data center space on the same site.

“To meet the needs of our growing business, we have decided to go ahead with the second phase of the project, which was an option we put in place when we broke ground earlier this year. The second phase should be finished by early 2012,” Tom Furlong, Facebook director of site operations, said on the company’s website Friday.

Facebook said it employs 150 to 200 workers each day at the construction site. The data center itself will create 35 long-term jobs.

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