An insider at JPMorgan Chase & Co has supplied a large amount of information to the U.S. Justice Department related to the sale of mortgage securities, which is using the documents to pursue possible criminal charges against the bank, the Wall Street Journal reported citing people familiar with the matter.
The cooperating person has provided information including emails suggesting that JPMorgan vastly overstated the quality of mortgages that it packaged into securities and sold to investors before the financial crisis, the newspaper quoted the sources.
(Read More: Dimon visits WhiteHouse amid settlement talks)
The sources declined to identify the insider or say whether the individual was still employed at JPMorgan, the report said.
The documents and other material provided by the insider have proved critical to the Justice Department's investigation and are fueling the government's aggressive push to elicit an admission of wrongdoing by JPMorgan as part of any settlement, the Journal said.
(Read More: JPMorgan's Jamie Dimon meets with AG at US Justice Department)
JPMorgan is seeking a "global" settlement of federal and state mortgage-related probes that could involve a payment of $7 billion in cash plus $4 billion for consumers, Reuters reported on Monday, citing people familiar with the negotiations.
JPMorgan could not immediately be reached for comment by Reuters outside of regular U.S. business hours.
—By Reuters