Seattle city officials have been approached by a private group looking to build a basketball arena in the Sodo District near Safeco Field in the hopes of attracting an NBA franchise, according to two sources who have been briefed on the talks.

The proposal involves an investor who has acquired property, apparently south of Safeco Field, although at least one business owner has declined to sell, according to the sources.

Mayor Mike McGinn has been working with the group for several months to explore how the city can aid the effort, including help with financing, the sources said.

McGinn's office confirmed Friday night that it is examining an "opportunity," but declined to provide specific information.

"Our office has had many enthusiastic overtures concerning the return of an NBA franchise to Seattle," the statement said. "Some of these offers have been serious. Some have not been serious. And the current speculation is over one of these proposals. We are looking at this opportunity, examining its specifics and how it fits our city. At this point, we have not received a concrete offer."

The statement added: "When we do reach that point, the City Council will be our first step in moving forward and then there will be an open process to evaluate that offer before we move forward. We would welcome a serious commitment from the NBA to re-establish a franchise with responsible ownership, to our community."

The proposal, the most detailed to surface since the Seattle Sonics left in 2008 for Oklahoma City, appears to be yet another attempt to revive the dream of an NBA team in the region.

McGinn has expressed an interest in the city playing a role in the financing, one of the sources said, noting the controversy that would generate. In 2006, Seattle voters overwhelmingly approved an initiative that says the city must make a profit on any investment it makes in a sports arena.

A new arena has been considered essential to acquiring an NBA team.

If an arena site were found and financing for the project obtained, investors would have to work with the NBA to attract a new franchise or buy an existing team, such as financially struggling teams in Sacramento and New Orleans.

The group behind the Sodo effort is separate from a recently publicized campaign being led by longtime Sonics fan Brian Robinson and his organization, Arena Solution, to secure a new arena and an NBA team.

Among those involved in the Sodo plan is Wally Walker, the former Seattle Sonics player and team executive, the sources said. Walker was a minority owner of the Sonics, serving as the team's president and general manager from 1994 until the team was sold to Clay Bennett in 2006.

Walker could not be reached for comment Friday.

Bennett moved the team to Oklahoma City after failing to secure a new arena in Seattle and reaching a financial settlement with the city of Seattle. Bennett said KeyArena, where the Sonics played, lacked the amenities required to support an NBA franchise.

If built, the arena would add a third professional sports facility in the Sodo District, joining Safeco, home of the Seattle Mariners, and CenturyLink Field, home of the Seattle Seahawks.

Other sites also have been mentioned as possible locations for an arena, notably Bellevue.

Microsoft CEO Steve Ballmer led an investment group that expressed a desire to buy the Sonics in 2008 to keep the team from leaving. The group failed to attract sufficient public funding to finance a new arena.

Speaking at a Rotary luncheon in July, Ballmer said a suitable arena would cost between $300 million and $500 million.

"I'm sure we'll someday wind up with that problem solved and with a basketball team back here in Seattle," he said.

Many think a new arena would have to offer both professional basketball and hockey to be a viable business proposition.

Seattle has never had an NHL team, though in 1990 a group led by then Sonics-owner Barry Ackerley, who died this year, sought to acquire an expansion franchise, but withdrew its bid.

KeyArena was not designed to meet NHL specifications when it was renovated in the mid-1990s.

Seattle Times reporter Eric Pryne and news researcher Miyoko Wolf contributed to this story, which also contains information from Seattle Times archives.

Steve Miletich: 206-464-3302 or smiletich@seattletimes.com