CME Group Inc. raised margins late Friday on its 5,000-ounce silver futures by 15.6 pct on Friday, the first since May. In late April and early May margins were lifted five five times by a total of about 84 percent.

CME, whose COMEX contracts are the world's leading precious metal futures, raised margins to $24,975 per contract from $21,600 effective after the close of business on Monday, Sept. 26.

Silver futures suffered their biggest one-day decline since 1987 on Friday, falling 18 percent. Silver futures settled at $30.05 an ounce as investors shed positions fearing silver had grown overly speculative.