Birmingham have confirmed a takeover approach from a company headed by Hong Kong businessman Carson Yeung.
Grandtop International Holdings bought an initial 29.9% stake in June 2007 but failed to complete a buyout.
"As shareholders will be aware, previous approaches did not proceed," said Birmingham in a statement.
"The issue of the funding of any possible offer will be a major factor in determining how the company responds to the approach."
The statement added: "The board of Birmingham note the recent press speculation and confirm they have received an approach from Grandtop International Holdings Limited ('Grandtop') - which may or may not lead to an offer for the entire issued share capital of the Company.
"Grandtop is currently a 29.9% shareholder, having acquired this holding in 2007. A further announcement updating shareholders will be made when appropriate."
Yeung was heavily criticised by the Birmingham board for not completely buying out chairman David Gold and co-owner David Sullivan, who terminated discussions with Grandtop in December 2007.
Gold claimed the uncertainty over Yeung's long-term plans cost the Blues the services of manager Steve Bruce, who left St Andrew's to take over at Wigan in November 2007.
Bruce kept the Latics in the Premier League, while Birmingham were relegated to the Championship under his successor Alex McLeish.
Yeung had been set a deadline of 21 December 2007 to complete his buy-out, but the Blues released a statement to the Stock Exchange on 20 December 2007 to announce that discussions had been terminated.
McLeish led Birmingham back into the Premier League with automatic promotion from the Championship in May 2009.
