NEW YORK/BOSTON (Reuters) - Some of the biggest U.S. mutual and hedge funds, including Daniel Loeb's Third Point and Daniel Och's Och-Ziff Capital Management OZM.N, owned stakes in Snap Inc SNAP.N, parent of the wildly popular Snapchat messaging app, at the end of March, regulatory filings on Friday showed.

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The filings provide the first definitive snapshot on who bought Snap shares when it went public in early March, in the biggest initial public offering for a U.S. tech company since Facebook Inc's FB.O 2012 debut.

While the shares quickly rose after the IPO, they plunged this week after Snap reported a $2.2 billion first-quarter loss. User growth and revenue fell short of some Wall Street estimates as it competed with similar apps.

On Wednesday the shares tumbled 23 percent in after-hours trading, wiping some $6 billion from Snap’s market value.

The quarterly disclosures of asset manager stock holdings, in what are known as 13F filings with the U.S. Securities and Exchange Commission, offer clues on what big investors are selling and buying, but give no indication of their current stakes.

Fidelity was the biggest owner of Snap with 33.4 million shares as of March 31, the filings show. Mutual fund powerhouse Vanguard owned 6.7 million. Loeb’s Third Point owned 2.25 million shares and OZ Management held roughly 1 million shares.

BlackRock Inc BLK.N, the world's largest asset manager with $5.4 trillion in assets, bought 9.4 million Snap shares during the first quarter, the asset manager's filing showed.

BlackRock, which has been vocal on several corporate governance issues including owners’ right to weigh in on a company’s policies, has not publicly commented on Snap shares’ lack of voting rights. A spokesman said the company does not comment on individual stocks.

The filings do not show which BlackRock funds held the Snap shares. None of the company’s mutual funds or exchange-traded funds have disclosed a position in the company yet.

David Tepper’s Appaloosa Management, which has $17 billion in assets under management, owned 100,000 Snap shares at the end of March.

A few days after Snap went public, Tepper, whose views on the market are closely watched, said he had trimmed his position as the stock price ran up and conceded that he might buy more at lower prices.

Appaloosa's filing also showed the firm cut its stake in Allergan Plc AGN.N by 31.1 percent to 2.9 million shares. Appaloosa also went back into General Motors Co GM.N in the first quarter with 5.2 million shares, as David Einhorn's Greenlight Capital calls for the automaker to dramatically change its capital structure by splitting its stock into two classes as part of a new capital allocation plan.

In early 2015, Tepper joined a group that was publicly agitating for a board seat to get GM to repurchase some of its shares.

A spokesman for Tepper declined to comment on Appaloosa’s filing.