U.S. prosecutors have broadened their criminal investigation of the Bernard Madoff case beyond the friends and family of the confessed swindler to at least eight investors and associates, The Wall Street Journal reported on Monday, citing people familiar with the matter.

The paper named three investors under investigation by the U.S. Attorney's Office, including Jeffry Picower and Stanley Chais, two philanthropists who are the target of lawsuits brought by the trustee liquidating the Madoff firm.

Carl Shapiro, a women's clothing entrepreneur and close friend of Madoff, is also under criminal investigation, the article said.

Investigators have gathered evidence of Picower and Chais telling Madoff how much in returns they wanted and that their accounts would reflect the amounts, the paper said. It said investigators were also reviewing evidence suggesting Shapiro knew his returns were fraudulent.

The paper said prosecutors have not charged any Madoff investors with criminal wrongdoing.

The Journal quotes a lawyer for Chais, 82, and a representative of Shapiro, 96, as saying the men had no knowledge of the fraud. A lawyer for Picower, 67, told the paper his client was not complicit in the scheme and had suffered billions in losses.

Madoff, 71, has pleaded guilty to 11 criminal charges including securities fraud, money laundering and perjury for a scheme in which he used money deposited from new clients to finance the withdrawals of earlier customers.

The scheme fell apart as a wave of clients sought to withdraw their money in 2008 amid the financial crisis.

Five months after Madoff's massive fraud was revealed, little of his victims' money has been found, and it appears increasingly likely that the worldwide hunt for their missing billions will drag on for years.

Reuters was unable to contact the U.S. Attorney's office for the Eastern District of New York outside regular business hours.

(Reporting by Anurag Kotoky in Bangalore; Editing by Lisa Von Ahn)