NEW YORK—Sotheby's said on Friday that it lost an additional $10.6 million from guarantees in its contemporary art auction last week, Bloomberg reports. The figure brings the auction house's total guarantee-related losses to $52.6 million in the last two months.

Two weeks ago, the house disclosed that it had suffered $42 million in guarantee losses from its Hong Kong sale, its contemporary art sale in London, and its New York Impressionist and modern sale. Shares fells 84 cents, or 8.7 percent, to $8.85.

Sotheby's has said in the past that it extends guarantees jointly with undisclosed third parties. In Friday's U.S. Securities and Exchange Commission filing, the house valued its share of the unsold guaranteed works at $16 million.

The $10.6 million in losses will be reported in Sotheby's fourth-quarter results.