WASHINGTON – Lawmakers are trying to learn the cause of the drastic stock market sell-off to ensure that high-tech trading is monitored and average investors are protected in the wilds of Wall Street.

Sens. Ted Kaufman, D-Del., and Mark Warner, D-Va., are working with Senate Banking Committee members to use a pending financial regulation bill to address the Dow Jones industrial average’s sudden, brief drop of almost 1,000 points Thursday. The House has scheduled a hearing on the sudden plunge for Tuesday.

President Obama said Friday that regulatory authorities are evaluating the “unusual market activity” with an eye toward protecting investors and preventing a recurrence. He said regulators will make their findings and recommendations public.

Warner and Kaufman want to use the financial overhaul bill moving through the Senate to insist that the Securities and Exchange Commission and the Commodity Futures Trading Commission undertake a thorough study of high-frequency trading and other tools that move markets in the blink of an eye.

“We saw a living, breathing, real-time example today of the potential catastrophe that takes place if we don’t have an ability to make sure we adequately use this technology,” Warner said late Thursday. “We must have safeguards and really realize how some of these firms are using this technology to get an advantage over the everyday main street investor.”

“Right now, there is no way to know what is happening in this marketplace,” Kaufman said.

In the House, Rep. Paul Kanjorski, D-Pa., has called for a Tuesday hearing of a subcommittee to examine the causes of the sudden freefall and partial rebound, some of the most volatile trading in market history. Kanjorski has asked SEC Chairwoman Mary Schapiro to investigate the causes of Thursday’s gyrations.

The startling market dive and bounce came amid doubts over Greece’s ability to confront its national debt and overarching stock market nervousness.

It also came as the Senate moved fitfully through a massive bill to put restraints on the financial sector.

The Wall Street plunge was unlikely to alter the outlook for the bill, which at this stage appears to be clearing a path for itself toward passage.

But the Senate has yet to address other aspects of the bill, including a bipartisan proposal to audit the Federal Reserve’s emergency loans to banks during the months leading to and after the 2008 financial crisis.

Republican senators have also proposed to strike a provision in the legislation that would force banks to spin off their business in derivatives, the complex securities blamed for helping precipitate the meltdown a year and a half ago.

Their position received a boost from former Federal Reserve Chairman Paul Volcker this week.

Volcker, in a letter to key senators dated Thursday, said banks should be permitted to provide derivatives to customers “in the usual course of a banking relationship.”

Volcker is an economic adviser to the White House and has advocated that commercial banks be prohibited from engaging in speculative trades with their own accounts.

But the financial regulation bill would go further by incorporating a provision sought by Sen. Blanche Lincoln, D-Ark., that would force banks to give up not only their own trades but also the business of creating the financial products for clients.