Republican Sen. Charles Grassley is investigating about 20 instances of suspicious trading by the hedge fund SAC Capital, a spokesman for the senator confirmed Saturday.

Grassley, R-Iowa, requested the information about the trades from the Financial Industry Regulatory Authority (FINRA), an independent regulator of brokerage firms. SAC is a large Stamford, Conn.-based hedge fund founded by billionaire Steven Cohen.

Grassley's inquiry comes amid a massive government investigation into insider trading at hedge funds. Two former SAC portfolio managers have pleaded guilty to securities fraud.

Last month, one of them, Donald Longueuil, admitted that he conspired from 2006 to 2010 to learn secrets about technology companies and trade on the information before it became public. He also confessed to destroying or throwing out a flash drive and hard drives after learning about the government's investigation.

No charges have been brought against SAC or Cohen.

In April, Grassley, who has long criticized government regulation of Wall Street, requested information about the SAC trades from FINRA. News that the regulator has sent the information to Grassley was first reported by The Wall Street Journal and was confirmed by Grassley's spokesman, Jill Kozeny.

SAC representatives met May 10 with Grassley's investigators. "We welcomed the opportunity to meet with the staff to educate them about the firm and our compliance efforts, and had an entirely appropriate, professional and cordial meeting," said SAC spokesman Jonathan Gasthalter. "We will continue to cooperate in any way we can."

The investigation into SAC is part of a broad probe into insider trading practices. Billionaire hedge fund founder Raj Rajaratnam was convicted this month on five counts of conspiracy and nine counts of securities fraud in the biggest insider trading case in decades. Rajaratnam made a fortune enticing corporate tipsters to feed him illegal information that gave him an edge in blockbuster trades.