U.S. securities regulators are investigating at least nine mergers, including Pfizer Inc's
takeover of Wyeth and Merck & Co Inc's acquisition of Schering-Plough Corp, for possible insider-trading violations, the Wall Street Journal reported, citing people familiar with the matter.

The Securities and Exchange Commission is probing whether deal advisers and traders illegally shared confidential information, the paper said, noting that the agency had sent out about three dozen subpoenas to hedge funds and brokerages.

It was 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.

It was not clear whether the subpoenas were related to the insider-trading case unveiled in October involving New York hedge fund Galleon Group, the paper said.

The Journal said some of the recent subpoenas focus on specifics of investment bankers' involvement in deals, including Goldman Sachs Group Inc bankers' roles in roughly a dozen health-care transactions since 2006.

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

Goldman Sachs has robust policies and procedures in place to detect suspicious trading activity. If we detect suspicious activity of any kind, as required by law, we report it to the appropriate authorities, a company spokesman told the paper.

The Journal said representatives for Eli Lilly, Napster and Wendy's/Arby's Group declined to comment and that a spokesman for JER Partners said the firm cooperated with an SEC inquiry involving the Genesis HealthCare deal in 2007, but JER Partners has not heard from the SEC this year. He told the paper Genesis executives were contacted by the SEC this year, but it was not clear whether that inquiry was connected to the recent subpoenas.

Pfizer, Merck, Abbott, Best Buy, Ansys and Genesis did not respond to the paper's requests for comment.

The SEC was not immediately available for a comment. The companies could not immediately be reached for a comment by Reuters.

(Reporting by A.Ananthalakshmi in Bangalore; editing by Simon Jessop and Gerald E. McCormick)