Internal Revenue Service agents searched the McLean home of former representative Robert P. Hanrahan (R-Ill.) Wednesday as part of a nationwide investigation of drug-related money laundering, the IRS said yesterday.

In a news release, the IRS said it had conducted a two-year undercover investigation of alleged conspiracy to defraud the government by making false statements and filing false currency transaction reports. Federal law requires banks and other financial institutions to report all cash transactions of $10,000 or more to the IRS.

The IRS said it had obtained criminal indictments and complaints against two banks and 11 persons in Dallas, New Orleans, Tulsa and Los Angeles. The agency said it also had executed eight search warrants in the Washington area, Massachusetts and Texas.

According to court documents, the Washington area search was conducted at Hanrahan's residence at 7268 Evans Mill Rd. Hanrahan has not been charged in the investigation.

Hanrahan, who served in the House from 1973 to 1975, said yesterday he was unaware of the investigation.

"The first I heard about it was what you just said to me," Hanrahan said. He referred questions to his attorney, Mark Damisch of Chicago, who declined to comment.

After leaving the House in 1975, Hanrahan served in the Ford administration as a deputy assistant secretary of health, education and welfare, and he was a Lake County, Ill., commissioner from 1980 to 1982. He is also a former executive of the Tobacco Institute and the American Security Council.

According to the news release, criminal charges were filed against the Premier Bank of Dallas, the Limestone National Bank of Sand Springs, Okla., and 11 persons in Texas, Oklahoma and Louisiana.

"The individuals and banks are charged with laundering several million dollars of currency purportedly from drug trafficking supplied to them by an undercover IRS agent," the IRS said.

The release said the criminal charges include violations of a 1986 law that is designed to make it a crime to divide cash transactions into amounts less than $10,000 to prevent the filing of the cash reports.