NEW YORK (CNNMoney.com) - Sotheby's largest shareholder has sold its stake in the art auction house, a move that suggests the booming art market may be cooling, according to a report published Wednesday.

Ariel Capital Management dumped its 12.3 percent stake after snapping up the company's stock in 2002, the Financial Times reported.

"We still think very highly of the company and its management," Tim Fidler, research director at Ariel, told the newspaper. "We just don't think the stock is very cheap anymore."

Sotheby's shares, which are hovering near a six-year high, have climbed 70 percent during the past year, the newspaper reported.

Substantial price increases in the Asian, contemporary and Old Masters artwork categories have led some to wonder whether the booming art market is due for a slowdown, according to the newspaper.

The move by Ariel marks the second time a major shareholder trimmed its holdings in the auction house. In September, the Taubman family, which controlled a substantial portion of the firm, slashed its 22 percent stake in outstanding shares and 60 percent control of voting shares to 12.4 percent in both categories, the Financial Times reported.

Shares of Sotheby's (Research) fell 4.8 percent to close at $28.54 Tuesday on the New York Stock Exchange.

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