Update 1: Jamie Dimon says exposure may result in more losses in future months.
Update 2: Dimon calls trade: "flawed, complex, poorly reviewed."
Update 3: Dimon says volatility will be high, will be risky for a couple of quarters
Update 4: JPMorgan shares down 6.38% in after hours trading at 5:27 ET
Update 5: JPMorgan's official announcement is that it lost $2 billion in a trading portfolio designed to hedge against risks the company takes with its own money. As a result, that segment of its business is expected to record a second-quarter loss of at least $800 million.