CHICAGO (Reuters) - Federal criminal investigations into failed mortgage lenders IndyMac Bancorp and New Century Financial corp have stalled, and a third probe into Washington Mutual Inc (WaMu), has ended with no charges being filed, the Wall Street Journal reported on Saturday.

Both the IndyMac and Century Financial investigations were essentially dormant, the newspaper said, citing people familiar with the situation. Both probes could still gain new momentum if fresh evidence surfaced, the newspaper said.

The three investigations were among the first to weigh criminal charges against the companies and executives at the heart of the U.S. housing crisis, which was in part caused by offering so-called sub-prime loans to people who may not have otherwise qualified for credit.

The U.S. Attorney's office in Los Angeles, which initiated the IndyMac and New Century probes, could not be reached for comment.

The U.S. Attorney's office in Seattle on Friday said that it had closed its investigation into WaMu, the newspaper said. A spokeswoman for that office could not be reached for comment.

The three lenders were overwhelmed by bad loans during the housing crisis. IndyMac and WaMu were seized by federal regulators in 2008 and New Century collapsed into bankruptcy in 2007.

Investigators have struggled to prove intentional wrongdoing, which is required to secure a conviction, particularly in relation to decisions signed off by in-house lawyers, the newspaper said, citing its sources.

(Reporting by Brad Dorfman; Editing by Paul Simao)