JPMorgan Chase, the biggest US bank, has revealed a surprise trading loss of $2bn on complex investments made by its traders.

美国最大的银行摩根大通银行的贸易商在复杂的投资中离奇地损失了20亿美元。

Overall, after accounting¹ for other gains, losses at its chief investment office (CIO) are estimated to come in at $800m in the second quarter.

The loss could be as big as $1bn, chief executive Jamie Dimon said in an unscheduled conference call.

JPMorgan shares fell 6% after-hours, with other bank stocks following.

Goldman Sachs, Citigroup and Bank of America also suffered heavy losses in electronic trading after the market close.

The strategy taken at its CIO had been "riskier², more volatile³ and less effective" than previously⁴ believed, Mr Dimon said.

"There were many errors, sloppiness⁵ and bad judgement. These were egregious⁶（惊人的） mistakes.

"They were self-inflicted and this is not how we want to run a business."

'Moving on'

The CIO is an arm of the bank used to make broad bets to hedge its portfolios⁸ of individual holdings. Hedging is an investment practice used to reduce the risk of price fluctuations⁹（价格起伏） to the value of an asset.

The trading loss, revealed in a regulatory filing, is expected to hurt JPMorgan's overall earnings¹⁰ in the quarter, and will come as an embarrassment¹¹ to the bank.

It had emerged from the 2008 financial crisis in much better health than many of its rivals after avoiding risky¹² investments that had hurt others.

"We will admit it, we will learn from it, we will fix it, and we will move on," Mr Dimon said.

He added that the bank was trying to unload the portfolio⁷ in question in a "responsible" manner in order to minimise the cost to shareholders¹³.