Other big investors previously seen as swing votes, such as State Street Corp, Bank of New York Mellon Corp and Invesco also voted their shares in favor of the deal on Wednesday night, the eve of the shareholder meeting, the person said.
The deal still needed another 150 million shares to pass as of early Thursday morning, but votes were still coming in and the tally could change before voting ends, the person said, requesting anonymity because the matter is not public.
The proposed buyout needs about 735 million shareholder votes to pass.
Representatives of all the investment firms were not immediately available for comment.
Dell shareholders were set to gather in Texas on Thursday to vote on founder Michael Dell's $24.4 billion offer to take the company private, a deal that faces heavy opposition from activist Carl Icahn and other investors.
T.Rowe Price Group Inc, Highfields Capital Management, Pzena Investment Management and Yacktman Asset Management are among the shareholders that have voiced opposition to a deal they say undervalues the company.
(Also see: Dell takeover battle: All you need to know)
© Thomson Reuters 2013