Blackstone Group LP has raised more than $6 billion for a real estate opportunity fund, which eventually could match its current $11 billion fund, a source familiar with the matter said on Tuesday.

An opportunity fund invests in properties that yield the highest returns as a reward for carrying the greatest risk.

In today's low-interest environment, opportunistic investments yield returns in the high teens, although that is not necessarily the parameters of Blackstone's funds.

A representative from Blackstone could not be reached for immediate comment.

Fundraising for many new private equity funds has been difficult after the real estate downturn destroyed the returns that some institutional investors had counted on to reinvest. Many investors have been steering their money to veteran investors with proven track records, such as Blackstone.

On Monday, developer Related Companies said it closed its first distressed real estate asset fund, raising $825 million, or $75 million more than its target goal.

In the past, Blackstone's real estate arm, Blackstone Real Estate Advisors, has raised opportunistic funds used to buy distressed debt and non-distressed properties such as its landmark 2007 buyout of Equity Office Properties.

The story was first reported by Bloomberg.

Blackstone Real Estate Partners VII fund, is expected to close its fundraising in February 2013, the source said. Most of Blackstone Real Estate Partners VI fund was invested in U.S. properties such as mall owner General Growth Properties Inc and Extended Stay hotels.

(Reporting by Ilaina Jonas; Editing by Gary Hill)

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