Google is expanding its 29,000-square-foot office next to Little Caesars Arena.

But by how much and when, and how many more employees the Mountain View, Calif.-based company is increasing by is not known.

A source familiar with the deal said those decisions about the future of its presence in the new office building at 52 East Henry Street next to the home of the Detroit Red Wings and Detroit Pistons have not yet been made.

Google, which officially unveiled its new office in November, has exercised an option to expand beyond its current approximately 29,000 or so square feet, according to a Detroit Economic Growth Corp. document. That space is on the third and fourth floors, the source said.

It is expected to take more space in the second floor, although the exact amount hasn't been determined.

The company currently has about 100 mostly sales employees in the office, which replaces its former outpost in downtown Birmingham. It moved from about 17,000 square feet in downtown Birmingham at Willits Street and North Old Woodward Avenue in a building owned by Boston-based International Real Estate Corp.

"Google Detroit is loving being part of the city and their home alongside LCA. Google is not able to comment further at this time," said Sara Wurfel, a spokeswoman for the tech giant and vice president of public affairs for public relations firm Truscott Rossman, which has an office in Detroit and is based in Lansing.

Eric Yuhasz, Google's facilities manager for Michigan, told Crain's in November that the Detroit office has capacity for another 25 hires and the lease with the Ilitches allows for more space on demand.

An email was sent to a spokesman for Olympia Development of Michigan, the Ilitch family's real estate arm.