Rather than disclosing the full extent of problems like fraudulent home appraisals and overextended borrowers, the bank adjusted the critical reviews, according to documents filed early Tuesday in federal court in Manhattan. As a result, the mortgages, which JPMorgan bundled into complex securities, appeared healthier, making the deals more appealing to investors.

The trove of internal e-mails and employee interviews, filed as part of a lawsuit by one of the investors in the securities, offers a fresh glimpse into Wall Street’s mortgage machine, which churned out billions of dollars of securities that later imploded.
The documents reveal that JPMorgan, as well as two firms the bank acquired during the credit crisis, Washington Mutual and Bear Stearns, flouted quality controls and ignored problems, sometimes hiding them entirely, in a quest for profit.