Corrects date of filings to September 30 in 7th paragraph and name of fund in last paragraph to New Horizons)

BOSTON - Online deal site Groupon is still privately held but retail investors might soon be able to own a piece of it, judging by other startups in which mutual funds run by T Rowe Price Group have invested.

The Baltimore asset manager is among a group of companies in talks to buy stakes in Groupon, according to the New York Times' DealBook.

The fast-growing online-advertising business on Thursday disclosed it has raised $500 million so far as part of an effort to raise up to $950 million in financing.

A T Rowe Price spokesman said it would not comment. Nor would another big asset manager, Boston's Fidelity Investments, which was also named as being in talks with Groupon by DealBook and by TechCrunch.com.

Fidelity has been known to buy into startups through its private investment arm, and hold those stakes apart from its traditional mutual funds. T Rowe, by contrast, often puts startup stakes into regular mutual funds that retail investors can buy.

Twitter, the hot microblogging service, last year identified T Rowe as among its investors. Regulatory filings show that at least three T Rowe funds bought shares in Twitter in September 2009.

These include the New Horizons Fund, which bought Twitter shares valued at $15.3 million; the Science & Technology Fund, which bought $7.4 million worth of the shares; and Global Technology Fund, which bought $559,000 worth. The figures come from third-quarter filings for each fund as of September 30.

The stakes make up just slivers of each funds' assets, which tend to concentrate on established technology companies like Microsoft Corp and International Business Machines Corp.

The Science & Technology Fund was once run by Roger McNamee, who later co-founded San Francisco private equity firm Elevation Partners, an investor in companies including Facebook and local search site Yelp Inc.

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