As reported by Reuters, trading of shares of The Washington Post Co (WPO.N)  was temporarily halted today after it triggered the first use of the new circuit breaker rule approved by the SEC on June 10 in response to the market disruption of May 6, specifically the “flash crash” that exposed the potential flaws in electronic trading.

As discussed in a previous Compliance Avenue blog (see SEC Approves New Stock-by-Stock Circuit Breaker Rules), the new rule requires the exchanges and FINRA to temporarily pause trading in any stock that moves 10 percent or more in the previous five-minute period.

“The halt was triggered by an erroneous trade,” said NYSE Euronext spokesman Ray Pellecchia, adding this was the first time the circuit breaker was activated.

According to Reuters, the newspaper’s Class B shares shot to $919.18 a share at 3:07:30 p.m. on the Pacific Stock Exchange in a trade of 400 shares that was immediately followed by a trade at the same price of 200 shares.

A third trade of 166 shares at $929.18, or $10 higher than the two previous trades, registered before the trading halt occurred, according to Thomson Reuters data.

The last trade registered before trading paused was at $455.14. Trading resumed a few minutes later.

The new circuit breaker rule, which is currently in effect on a pilot basis until December 10, 2010, applies only to stocks that are components of the S&P 500® Index.  The pilot period is meant to allow the markets to make appropriate adjustments to the parameters or operation of the circuit breakers as warranted based on their experience, and to expand the scope to securities beyond the S&P 500 (including ETFs) as soon as practicable.

As stated by SEC Chairman Mary Schapiro:

“It is my hope to rapidly expand the program to thousands of additional publicly traded companies.”