<!-- IMAGE -->
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, a congressional committee, and some members of the Senate 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.
<!-- IMAGE -->