Apple is significantly expanding its downtown Seattle engineering center, giving itself enough capacity for potentially close to 500 people across five floors inside one of the city’s tallest skyscrapers, GeekWire has learned.

The expansion by the secretive tech company is the latest sign of the ferocious competition for tech talent in the Seattle region, where fellow tech titans Amazon, Microsoft, Google and Facebook all have larger footprints.

Apple is preparing to move into another floor at Two Union Square, a 56-story office tower in downtown Seattle, giving it all or part of five floors of the building, GeekWire has learned through permitting documents and visits to the building. The latest move brings Apple to more than 70,000 square feet, which equates to room for somewhere between 350 and 475 people, based on standard corporate leasing ratios for tech companies.

With these moves, Apple is following through on a plan to expand its Seattle presence, first reported by GeekWire last year.

Apple established its first formal engineering office in Seattle with its 2014 acquisition of Union Bay Networks. A year later, it leased a floor and a half at Two Union Square. In 2016, Apple acquired machine learning startup Turi, establishing the office as a hub for developing artificial intelligence and machine learning technologies.

The competition for artificial intelligence talent is especially intense. Facebook recently poached a highly regarded AI researcher from the Allen Institute for Artificial Intelligence, which is in the midst of a major expansion of its own. Microsoft is also doubling-down on AI as part of its latest restructuring.

Apple wouldn’t comment on its office space and doesn’t do much to boast about its presence. Its name isn’t listed on the main directory in the Two Union Square lobby. Most floors have little-to-no trace of Apple’s presence except key card readers outside entrances asking people to swipe their Apple ID badges.

RELATED CONTENT Check out GeekWire's list of Seattle-Area Engineering Centers established by out-of-town companies.

The company’s job site lists 19 open positions in its Seattle office. The jobs are in a variety of areas including machine learning, smart home, data science, cloud computing and natural language processing.

Apple is following an established blueprint of big tech companies opening engineering offices in the Seattle area to take advantage of the region’s deep talent pool. Fellow tech giants Google and Facebook are both prominent examples of that trend.

Google, based in Mountain View, Calif., first expanded to the Seattle region in 2004, and today it has more than 3,000 workers in the region. Google continues to scoop office space in Seattle’s Fremont neighborhood at every turn, even as work is underway on a new 600,000-square-foot campus in Amazon’s neighborhood.

Facebook opened its first Seattle engineering office in 2010, employing just a couple people near Pike Place Market. Last month Facebook opened a new 150,000-square-foot office building near Lake Union, two years after it debuted a big new office space designed by Frank Gehry. Those two structures have space for nearly 3,000 people combined. Facebook also recently leased another huge project, totaling 384,000 square feet just a few blocks from Amazon HQ.