FBI Director Robert Mueller told lawmakers that his agency won't hesitate to pursue top financial executives as it investigates the subprime mortgage meltdown.

The Federal Bureau of Investigation is now probing 24 large companies for possibly misstating their assets, Mueller told the U.S. House Judiciary Committee in Washington, up from 21 in July.

"The FBI will pursue these cases as far up the corporate chain as necessary," he said.

The FBI has come under pressure to hold companies responsible as the loan crisis has rocked Wall Street and led to the biggest housing slump since the Great Depression. The bureau also is conducting more than 1,400 smaller investigations aimed primarily at individuals including brokers, appraisers and borrowers, Mueller told the panel.

While Mueller didn't name any companies under scrutiny, people familiar with the matter have said they include IndyMac Bancorp Inc. and Countrywide Financial Corp., which has since been bought by Bank of America Corp.