Facebook is starting to look a little Amazon-like in the speed with which it is gobbling up Seattle real estate.

The social network has leased the 150,621-square-foot 1101 Westlake building in the South Lake Union neighborhood, according to a year-end report from real estate brokerage the Broderick Group.

Rumors have swirled about Facebook’s interest in 1101 Westlake for months. But then last month the company scooped up the Arbor Blocks, a pair of six-story structures that total 384,000 square feet of office space developed by Paul Allen’s Vulcan Real Estate.

The latest deal has Facebook approaching 1 million square feet of office space in Seattle.

Facebook’s latest expansion comes less than a year after the company opened its big new Frank Gehry-designed Dexter Station building, also in South Lake Union. It has room for up to 2,000 people, but apparently that wasn’t enough.

For years, Amazon was the main player in the South Lake Union neighborhood, but recently several of the world’s biggest tech companies have planted flags there as well. Google last year inked a huge lease from Vulcan, just a couple blocks from Facebook’s new digs. The first phase of the four-building campus could start early this year and open in the fourth quarter of 2018.

Facebook is perhaps the greatest example of how out-of-town tech companies are investing in Seattle. Facebook opened its first Seattle engineering office in 2010, near Pike Place Market, and later moved to occupy multiple floors in the Metropolitan Park complex near Interstate 5.

The company surpassed 500 employees in the Seattle office early in 2015, cementing its position as the company’s largest engineering center outside of its Menlo Park, Calif., headquarters. Including operations of Facebook-owned Oculus, the company said in May 2016 its Seattle headcount had exceeded 1,000 people.

More than 80 companies from around the world have followed the same playbook and set up shop here in the region, and many of them have grown to become big parts of the local tech ecosystem.

GeekWire has reached out to Facebook and we’ll update this story when we hear back.