Mexico Exchange Said to Cancel Erroneous Trades of Slim’s Frisco

Mexico’s exchange has canceled some erroneous trades that caused shares of billionaire Carlos Slim’s Minera Frisco SAB to double in price, according to a bourse official with direct knowledge of the decision.

A technical glitch at the exchange prompted the silver and gold miner’s stock to soar as much as 104 percent in intraday trading yesterday, said the person, who asked not to be named because he hadn’t been authorized to speak on the matter. The shares pared their gain to 25 percent and closed at 36.29 pesos yesterday in Mexico City. The canceled trades had a volume of about 250,000 shares and took place in the 10 minutes of trading, the person said.

Roberto Gavaldon, a stock exchange spokesman, didn’t respond to a phone call and e-mail seeking comment on the trades. Aurelio Bueno, a press official for the National Banking and Securities Commission, said the nation’s regulator was reviewing the jump in Frisco’s price. Minera Frisco said in an e-mailed response to questions that the company has no knowledge of any reason for the share move.

The error occurred amid the exchange’s most-active trading day on record, according to volume data compiled by Bloomberg. Money managers had been updating their portfolios before changes on the benchmark IPC index take effect on Sept. 2. Five of the 35 stocks on the gauge, including Frisco, are getting replaced, while others will have their weightings adjusted.

The nation’s bourse implemented safeguards to limit damage from trading mistakes after a human-input error at brokerage Bulltick Capital Markets erased 2 percent from the benchmark index in three minutes in April 2012.

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