Advisors in the sale of a controlling stake in Hynix Semiconductor are tapping potential bidders as shareholders are now open to new bids for the world's No.2 memory chipmaker after STX pulled out, an official with one of the shareholders said.

Following its contender's withdrawal, the country's top mobile carrier SK Telecom was left as sole bidder for the stake, casing a shadow over shareholders' efforts to find a new owner after previous aborted attempts.

Lead shareholder Korea Exchange Bank said on Wednesday it would allow new bidders to participate in the stake sale in the interests of valid competition.

The 146.1 million shares on offer, including new shares, are worth at $2.5 billion at Friday's closing price.

The official said final bids were likely to be pushed back from late October.

New bidders will not be given a chance to conduct due diligence, as opposed to SK Telecom's seven-week inspection, sources with knowledge of the deal have said.

Nine shareholders of Hynix, including Korea Finance Corp, Korea Exchange Bank, Shinhan Bank and Woori Bank had planned to receive final bids around Oct 24.

Shares in Hynix Semiconductor rose 2 percent and SK Telecom also advanced 2 percent in a flat broader market as of 8:32 p.m. EDT.

The official added that the shareholders would this week discuss the details of an invitation letter to be sent out as late as early October.

Shareholders have scaled down their stake in Hynix but failed several times to complete a full sale, with investors avoiding a risky jump into the capital intensive, cyclical memory chip sector.