Brian Snyder/Reuters

F.B.I. agents raided the offices of three hedge funds on Monday, the government’s latest salvo in an escalating investigation into insider trading on Wall Street.

Two of the hedge funds, Level Global Investors of New York and Diamondback Capital Management of Stamford, Conn., are controlled by alumni of SAC Capital Advisors, also in Stamford, hedge fund colossus run by the billionaire Steven A. Cohen, who is known for his stellar returns and uncanny trading talents.

The third firm, Loch Capital Management, is a Boston hedge fund focused on technology investments .

More searches could be executed in the coming days, according to a person briefed on the investigation who spoke only on the condition of anonymity.

“We are conducting court-authorized search warrants as part of an ongoing investigation,” said Richard Kolko, a supervisory special agent at the F.B.I.’s New York office. “The matter is sealed. We have no further comment.”

No one at the firms searched by federal agents on Monday has been accused of wrongdoing. Neither Mr. Cohen nor SAC has been accused of wrongdoing. An SAC spokesman declined to comment.

A spokesman for Level Global confirmed that F.B.I. agents visited the fund’s offices and said that it was cooperating fully with authorities. A Diamondback spokesman said the firm received an F.B.I. inquiry and was voluntarily cooperating.

A lawyer for Loch Capital did not return telephone calls and e-mails seeking comment.

Taking the aggressive tack of using search warrants to raid the firms’ offices, rather than issuing grand jury subpoenas demanding the production of documents, suggests that federal prosecutors are concerned about the destruction of evidence related to possible crimes, lawyers say.

It is also possible that the government has already served these firms with subpoenas, and it is looking to scoop up any remaining documents.

“This guarantees that the government can quickly and securely get its hand on evidence,” said Fernando L. Aenlle-Rocha, a lawyer at White & Case and former federal prosecutor who is not involved in the investigation. “Tactics such as this tend to make people at the targets very nervous and may even prompt some employees to speak to government agents.”

The F.B.I. raids came after news media reports over the weekend that the Justice Department and the Securities and Exchange Commission were readying a round of criminal and civil charges related to insider trading.

This aggressive government tactic is part of a broader investigation of insider trading led by Preet Bharara , the United States attorney for Manhattan . Just over a year ago, Mr. Bharara’s office brought insider trading charges against Raj Rajaratnam , the co-founder of hedge fund Galleon Group.

Mr. Rajaratnam is fighting the charges and is expected to go on trial early next year. There have been 23 arrests and 14 guilty pleas in the Galleon case, which has been billed by prosecutors as the largest hedge fund insider-trading investigation in history.

At least one individual ensnared by the Galleon case has ties to SAC. Richard Choo-Beng Lee pleaded guilty to insider trading crimes related to activity after he left a unit of SAC, where he was a trader from 1999 through 2004. Jeffrey L. Bornstein, a lawyer for Mr. Lee, said his client was cooperating with the government in its insider-trading investigation.

Another cooperating witness in the Galleon case is Steven Fortuna, who pleaded guilty last year. Mr. Fortuna is an acquaintance of Timothy and Todd McSweeney, the brothers who run Loch Capital, Reuters reported this year. Both Mr. Fortuna and Mr. Lee had previously worked together at another hedge fund.

SAC has been a breeding ground for dozens of traders who have eventually formed their own hedge funds. Two of the largest and most successful are Level Global, which manages $4 billion, and Diamondback, which manages $5 billion. They have handily outperformed the Standard & Poor’s 500-stock index since their inceptions.

Mr. Cohen has been known to invest his personal money in his traders’ new ventures, but this was not the case with either Level Global or Diamondback. He does not have investments with either fund, said two people briefed on the matter who spoke only on the condition of anonymity.

Mr. Cohen has a family connection to Diamondback, which was partly founded in 2005 by the SAC alumni Richard Schimel, Lawrence Sapanski and Chad Loweth. Mr. Cohen’s sister Wendy, a former SAC trader, is married to Mr. Schimel.

Patrick McMullan/PatrickMcMullan.com

Level Global, partly founded in 2003 by David Ganek, is among the most high-profile of the SAC spinoffs. This year, a Goldman Sachs fund that purchases minority stakes in hedge funds bought a stake in Level Global. A spokeswoman for Goldman, which does not have an investment decision-making role at Level Global, declined to comment.

Like Mr. Cohen, Mr. Ganek is a prominent figure in the art world. He and his wife, the novelist Danielle Ganek, have a collection that is said to include works by Richard Prince and Jeff Koons . In 2004, they gave 13 prints by the photographer Diane Arbus to the Metropolitan Museum of Art in what the museum described as one of the most significant acquisitions of 20th-century photography in its history.

Mr. and Mrs. Ganek, fixtures on the Manhattan social circuit, also have an apartment at one of the city’s most exclusive addresses: they paid a reported $19 million in 2005 for a co-op at 740 Park Avenue, which is home to a who’s who of New York business and society, including Stephen A. Schwarzman , the private equity mogul, and Ronald Lauder, the cosmetics magnate.

The raids of Mr. Ganek’s firm and the other two hedge funds underscore the bold techniques being used by law enforcement in the pursuit of white-collar crime. In the Galleon case, many of the arrests resulted from wiretapped conversations of Mr. Rajaratnam and other stock traders. The Justice Department had never before used wiretapping to pursue insider trading, and Mr. Rajaratnam’s lawyers have asked the judge to prohibit the tapes from being used at trial.

Law enforcement officials at the highest levels of the Justice Department have in recent weeks publicly stated that they would continue to use more aggressive techniques when investigating business fraud.

“We have begun increasingly to rely, in white-collar cases, on undercover investigative techniques that have perhaps been more commonly associate with the investigation of organized and violent crime,” said Lanny A. Breuer, assistant attorney general of the Justice Department’s criminal division, in a speech this month.

The searches on Monday also suggest that this phase of the Manhattan United States attorney’s insider-trading investigation is nearing an end.

Ronald S. Safer, a lawyer at Schiff Hardin and former federal prosecutor, said these investigations typically consisted of two phases: the covert and the overt. The covert phase include tactics like wiretaps, which allow investigators to work quietly without tipping their hand. A raid alerts everyone to the fact there is an investigation.

“The overt phase is always a lot shorter than the covert phase,” he said. “You’ve got to think they are drawing toward the close.”

Thomas Kaplan and Edward Wyatt contributed reporting.