NEW YORK, AUG. 13 -- The Securities and Exchange Commission, in a broadened investigation stemming from the so-called "Yuppie Five" case, is probing possible insider stock trading by at least a dozen professional stock speculators here, sources familiar with the investigation said today.

But the sources said that despite broad inquiries made by the SEC, there is no indication that charges would be made soon by the government or that new targets -- other than the Yuppie Five and several people implicated by them earlier -- had been identified in the investigation.

"There has been a blizzard of subpoenas and a lot of testimony has been taken," said Bart Tiernan, an attorney for Kellner DiLeo & Co., one of the arbitrage firms that has had employes testify before the SEC. Arbitrage firms frequently speculate in the stocks of companies involved in corporate takeovers.

Tiernan emphasized that his firm has been told by the SEC that its investigators have completed their questioning and that no Kellner employes are targets of the continuing probe.

Other firms whose employes have been subpoenaed in the broadened probe include Oppenheimer & Co., Spear, Leeds & Kellogg, and Victor Teicher & Co., sources said. A subpoena is a request for information and does not imply any wrongdoing.

Sources said the titles of subpoenas issued by the SEC refer to trading by Marcus Schloss & Co., a Wall Street arbitrage firm that earlier employed Andrew Solomon, a young securities analyst who has pleaded guilty to insider trading charges along with four other lawyers and analysts. The ring has been referred to as the Yuppie Five, partly because all of the participants were young Wall Street professionals.

The leader of the ring has been identified as Michael David, a former associate at the New York law firm of Paul, Weiss, Rifkind, Wharton & Garrison. David, who pleaded guilty to insider trading charges last fall, has not yet been sentenced. David allegedly passed confidential information about upcoming takeovers gleaned from his work at Paul Weiss to Solomon and others who could use it to trade stocks.

Sources said that David, Solomon and a third man who was not charged with any wrongdoing, former Marcus Schloss compliance officer Arthur Ainsburg, have cooperated with the SEC investigation. The sources said the SEC is continuing to focus on allegations made by the three against two Marcus Schloss executives, Irwin Schloss and Ronald Yagoda. Attorneys for the two men have repeatedly denied any wrongdoing.

Schloss, Yagoda, and a third man under investigation by the SEC, Victor Teicher, are said by sources familiar with the probe to have given several depositions each to SEC investigators. None of the three has asserted his right to protection against self-incrimination under questioning, the sources said.

"It has been previously reported that governmental agencies are focusing on Mr. Teicher," his attorney, Robert Morvillo, said today. "Mr. Teicher has always denied any wrongdoing and is confident that at the conclusion of these investigations nobody is going to bring any formal accusations against him."

The source of the allegations being pursued by the government remains unclear, lawyers and others familiar with the investigation said. Sources said that neither David nor Teicher has been actively providing information to the government in recent months.

Many of those who have been questioned or subpoenaed in the probe are young traders at prominent arbitrage firms, sources said. Some of the traders are said to have known members of the Yuppie Five ring.

Typically, the sources said, SEC investigators have examined trading and telephone records, and sometimes asked questions, to determine whether inside information about upcoming takeover events was passed illegally to the traders