A new U.S. securities regulatory investigation into potential insider trading began in mid-November with the issuance of subpoenas to a number of hedge funds that may have gotten an advance word on corporate takeovers, said people familiar with the matter.

The subpoenas were issued by the Securities and Exchange Commission's Philadelphia regional office and also went to a number of Wall Street investment houses, the sources said.

The Wall Street Journal, which first reported on the investigation, said regulators are looking into reports of insider trading in at least nine mergers, including Pfizer Inc's takeover of Wyeth and Merck & Co Inc's acquisition of Schering-Plough Corp.

The paper reported that regulators have sent out about three dozen subpoenas.

Another deal under scrutiny is the 2007 acquisition of nursing home operator Genesis HealthCare Corp by private equity firms JER Partners and Formation Capital, according to the Journal.

The Genesis HealthCare acquisition already has led to one insider trading enforcement action brought by the SEC's Philadelphia office, which may explain why regulators there are heading up the investigation.

In 2007, the SEC charged Jennifer Xuija Wang and her husband, Ruben Chen, with insider trading by using "nonpublic information" to trade ahead of takeovers of Genesis HealthCare and two other companies. Regulators charged that Wang, who at the time was a Morgan Stanley vice president, passed on deal information she had gathered from her job to her husband.

The couple pleaded guilty to securities fraud charges in a related criminal case. A lawyer for Wang said she was not aware of the latest SEC investigation.

The Journal said a spokesman for JER Partners said the firm cooperated with the SEC's 2007 inquiry, but the firm had not heard from the SEC this year. However, he told the paper that Genesis executives were contacted by the SEC this year, but it was not clear whether that inquiry was connected to the recent subpoenas.

The SEC also is looking at other pharmaceutical deals including Abbott Laboratories Inc's acquisition of Advanced Medical Optics and Eli Lilly & Co's buyout of ImClone Systems, the paper reported.

The Journal also said the SEC is asking questions about trading around retailer Best Buy Co Inc's 2008 acquisition of Napster Inc, investment firm Triarc Cos' acquisition of Wendy's International Inc and Ansys Inc's takeover of Ansoft Corp.

The newest round of subpoenas comes in the midst of the biggest criminal insider trading case in two decades. To date, federal prosecutors have charged or taken guilty pleas from 20 people in the so-called Galleon Management insider trading case.

But a person familiar with the investigation said it is not directly related to the ongoing Galleon investigation, which largely has focused on the trading of nonpublic information about tech companies.

The Journal said some of the recent subpoenas focus on the involvement of investment bankers in deals, including bankers at Goldman Sachs Group Inc in roughly a dozen healthcare transactions since 2006.

Goldman was an adviser to Schering-Plough and Pfizer, according to filings cited by the Journal.

The Journal said representatives for Eli Lilly, Napster and Wendy's/Arby's Group declined to comment. Pfizer, Merck, Abbott, Best Buy, Ansys and Genesis did not respond to the paper's requests for comment. A spokesman for Goldman told the Journal that it has policies to detect insider trading and that it reports suspicious activity to relevant authorities.