Amazon is close to locking down one of the most high-profile office projects in the Seattle region, indicating that it is nowhere near done growing its Seattle presence.

The Rainier Square project is one of the biggest available blocks of space in the area, and three commercial real estate sources told GeekWire that Amazon has a “pending” lease for the entirety of the office portion of the mixed-use structure. That means the major points have been hashed out, sources said, and only final details remain.

The project, which shares a downtown Seattle block with the uniquely designed Rainier Tower, includes a 58-story office and residential building as well as a 12-story hotel. The office space totals 710,000 square feet on the lower floors, with 220 residential units above. The adjacent hotel has 165 rooms.

Greg Johnson, president of Wright Runstad & Co., the developer on the project, declined to comment on leasing details. Amazon representatives did not respond to a request for comment.

Johnson said construction is slated to begin in the next couple months. Due to the construction, all the retail in the existing Rainier Tower has closed.

The Puget Sound Business Journal previously reported that Amazon was interested in the space.

For awhile it seemed possible that the Rainier Square project would be an anomaly in Seattle, a big new office building not occupied by Amazon, or even Facebook. F5 Networks was interested in the structure before Amazon swooped in, sources said. F5 was looking at a number of properties and eventually landing at a project a few blocks south at Fifth and Columbia, which is now called F5 Tower.

For years, observers have wondered if or when Amazon will slow down. But that clearly isn’t happening anytime soon, as demonstrated by the numerous leases at new office towers in recent years, in addition to the millions of square feet the company is building as part of its new campus in the Denny Triangle area.

Amazon added another 31,000 employees in the most recent quarter, bringing its total global headcount to 382,400. On its website, the company is listing another 19,500 open positions. And today Amazon is hosting its first-ever “Amazon Jobs Day” at 10 of its fulfillment centers where interested folks can learn more about job opportunities.

Amazon’s home state of Washington boasts the largest concentration of employees at more than 40,000, a figure that doesn’t include seasonal workers. California, where Amazon just expanded with a big new lease in San Francisco, is second at more than 30,000 people.