U.S. President Barack Obama says regulatory officials are "closely" evaluating Thursday's drastic U.S. stock market decline.

He 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.  The Dow and other key indexes later recovered to post losses around three percent at the close of Thursday.

Experts were not sure what caused the incident.  A review was under way by the U.S. Securities and Exchange Commission, which is charged with ensuring fairness in the U.S. stock market.

Thursday's wild trading came amid concerns about the Greek debt crisis, which already had pushed stock values down several days in a row.

On Friday, the Dow fell 1.3 percent.  Investors are concerned about the situation in Greece, but encouraged by a report showing the U.S. economy created 290,000 jobs last month.