The trading losses suffered by JPMorgan Chase have surged in recent days, surpassing the bank’s initial $2 billion estimate by at least $1 billion, according to people with knowledge of the losses.

When Jamie Dimon, JPMorgan’s chief executive, announced the losses last Thursday, he indicated they could double within the next few quarters. But that process has been compressed into four trading days as hedge funds and other investors take advantage of JPMorgan’s distress, fueling faster deterioration in the underlying credit market positions held by the bank.

A spokeswoman for the bank declined to comment, although Mr. Dimon has said the total paper trading losses will be volatile depending on day-to-day market fluctuations.

The Federal Reserve is examining the scope of the growing losses and the original bet, along with whether JPMorgan’s chief investment office took risks that were inappropriate for a federally insured depository institution, according to several people with knowledge of the examination. They spoke on the condition of anonymity because the investigation is still under way.

The overall health of the bank remains strong, even with the additional losses, and JPMorgan has been able to increase its stock dividend faster than its rivals because of stronger earnings and a more solid capital buffer.

JPMorgan's Trading Loss Is Said to Rise at Least 50% - NYTimes.com