Brevan Howard Asset Management LLP, one of the Europe's biggest hedge fund managers, may return about $2 billion to investors in the firm's biggest fund to avoid growing too large, Bloomberg said, citing four people familiar with the matter.

The people, who asked not to be identified because the company is private, told Bloomberg that clients of the London-based firm's Master Fund, that oversees $26.9 billion, have said they want the fund to remain at about $25 billion, to avoid size hurting performance.

Brevan Howard could pick and choose which clients get their money back, or it could return money to investors in the fund on a pro rata basis, Bloomberg said.

The firm is unlikely to make long-term investors withdraw funds, Bloomberg reported one of the people as saying.

Brevan Howard did not immediately respond to emails seeking comment.

(Reporting by Arpita Mukherjee in Bangalore; editing by Richard Chang)