美国总统奥巴马说，监管人员正严密评估星期四美国股市暴跌的经过。
奥巴马说，监管人员对保护投资者，防止未来发生这样的混乱局面非常关注。
星期四道琼斯工业指数暴跌近千点。这导致世界股价下跌1万亿美元。后来美国股市有所反弹，星期四收盘时全天下跌大约3%。
美国证券交易委员会、美国财政部和至少一个国会委员会说，他们将审查此事。
媒体报导援引专家的话说，此次暴跌可能是由一个交易失误引起的，例如卖家本想抛售价值数百万的股票，但结果却抛售了价值数十亿美元的股票。
官员和调查人员还讨论如何更好地理解和监管许多瞬间交易巨额股票的电脑程序。他们的看法是，这些电脑程序或许将市场错误的影响放大了。
股市出现暴跌时，希腊的债务危机已经连续多日让股票价格下滑。
在星期五的交易中，欧洲重要股指-巴黎CAC 40-曾一度下跌5%，亚洲重要股指-东京日经指数-收盘时下跌3%。美国股市则在涨跌间波动。
U.S. President Barack Obama says regulatory officials are "closely" evaluating Thursday's drastic U.S. stock market decline.
The president says regulators are concerned about protecting investors and preventing such disorder in the future.
Thursday's nearly 1,000-point fall in the Dow Jones Industrial Average sparked a $1 trillion decline in stock values around the world. U.S. stock prices recovered somewhat, and were off by around three percent at Thursday's close.
The U.S. Securities and Exchange Commission, the Treasury Department, and at least one congressional committee have said they will be reviewing the matter.
Experts quoted in published reports say the drop might have been sparked by a trading error, such as selling billions of dollars' worth of stocks instead of the millions of dollars the seller intended.
Officials and investors also are discussing how to better understand and regulate the many computer programs that instantly trade huge volumes of stocks. The theory is that such programs may have magnified the impact of a market error.
All of this came against the backdrop of concern about the Greek debt crisis that already had pushed stock values down for several days in a row.
In Friday's trading, a key European stock market index (the CAC 40 in Paris) was off as much as five percent at one point, a major Asian index (the Nikkei in Tokyo) was down three percent at the close, and U.S. stock market indexes swung back and forth between losses and gains.
