NEW YORK ( TheStreet) -- AOL ( AOL) and several private-equity firms are in preliminary exploratory talks about making an offer to buy Yahoo! ( YHOO), the Wall Street Journal reports.

Yahoo! shares were rising 15.1% to $17.55 in premarket trading Thursday.

People familiar with the matter told the Journal that the discussions -- involving private-equity firms, AOL executives and financial advisers -- don't yet involve Yahoo! The conversations may not lead to an approach given the complexities in structuring a proposal, the people told the newspaper.

Silver Lake Partners and Blackstone ( BX) are among the firms that have expressed interest in teaming up with AOL to buy Yahoo! or trying to take it private on their own, the people said, the Journal reports. At least two or three other firms could be interested in participating if a formal buyout proposal is developed.

Spokeswomen for Yahoo! and AOL declined to comment for the newspaper.

AOL has a market capitalization of $2.68 billion, smaller than Yahoo's $20.56 billion market value, the Journal notes.

Bloomberg reports that Yahoo! was working with Goldman Sachs to help defend against possible takeover approaches. Bloomberg cited three people familiar with the matter.

While Yahoo! hasn't received an offer, it has been working with advisers for about two weeks to field any approach, said the people, Bloomberg reports.

-- Written by Joseph Woelfel

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