The owner of TCF Tower and Building in downtown Minneapolis expects to complete redevelopment plans for them within a month, the company said Wednesday.

Franklin Street Properties Corp., the Massachusetts-based real estate investment trust that owns the adjoined buildings, told investors it is making progress with several other firms on plans to build a 50-story tower on a portion of the site at Marquette Avenue and S. 8th Street

TCF Bank's lease on its namesake building officially expired last month, allowing Franklin Street to pick up speed, the firm said. In October, when the plans were unveiled, Franklin Street said it anticipated starting construction in the second half of 2016. The new tower would include a hotel, apartments and office space and be on a portion of the property now occupied by a four-story building. The adjacent, existing 17-story office tower would be updated as well.

In Wednesday's call with investors, executives reaffirmed their commitment to the project and local development partners and said they expect to finalize plans within the next month, presumably making them more public. As new construction in commercial real estate begins to show signs of slowing, any mention of the project is taken as a sign of the company's seriousness.

The company first announced a redevelopment team in 2014 that included Minneapolis-based developer and builder Ryan Cos., architectural firm Perkins+Will and leasing agency CBRE Group. Franklin Street has declined to name any of its partners recently.

The owner is working "in earnest" with its development and downtown partners on costing and feasibility right now, said Jeff Carter, executive vice president and chief investment officer. Franklin Street would maintain ownership of the office component in the proposed tower, contributing the land and $80 million to $90 million toward development costs. The hotel and apartment components, to be stacked atop one another, along with the office element, would each be owned by separate groups.

No design renderings or names of its hotel and residential developers have been released.

As for preleasing, "we have seen good activity" and "we evaluate as we go along," Carter said.

TCF Bank vacated space in both TCF Tower and TCF Bank Building, when it moved about 1,100 employees from downtown Minneapolis to a low-slung office building in Plymouth last year.

The move aligns with Franklin Street's strategy of selling off its noncore suburban office buildings and investing more in its urban properties. The two TCF properties are in Franklin Street's core portfolio.