By Chris Coates Staff Writer Citing a lack of space and overcrowded conditions at its headquarters, the biotech firm Amgen plans to move some of its Thousand Oaks administrative staff to a site in Colorado. Amgen spokeswoman Ashleigh Koss said departments affected include human resources, information systems and finance, although no specific numbers have been set. She said the company has outgrown its sprawling, 194-acre campus in Thousand Oaks, where the molecular researcher and medicine manufacturer was founded in 1980. “Our company is growing quite rapidly,” she said. “Here in Thousand Oaks, we’ve hit our maximum.” The moves are scheduled to happen over the next two years. Amgen has operated a manufacturing center Longmont near Boulder, Colo., since 1999. A new building on the campus is set to break ground next year, with completion slated for 2008. Amgen, with 2005 revenues totaling $12.4 billion, has seven facilities in the U.S. and 17,000 employees worldwide.