British banks RBS, Barclays, Standard Chartered and HSBC have been named in investigation.
Morgan analysts, led by Serena Tang, opined that in the most optimistic scenario, the gush could exceed $1.2tn.
Change in currency value mainly depends on demand and supply, as in case of anything else.
US Federal Reserve expected to hike interest rates this September, a negative for bullion prices.
IMF says appreciation over past year has normalised exchange rate of yuan.
The number of US rigs actively drilling for oil have now fallen for the 23rd week in a row.
Other major banks have paid billions of pounds to UK and US regulators over foreign currency manipulation.
Russia's ruble currency has increased in value around 18% since the turn of the year.
For gold to gain any strong momentum, prices have to break above resistance between $1,221 and $1,225 an ounce.
Weak US data to fuel speculation that US Fed will wait until September to hike rates, boosting gold's safe-haven status.
World Gold Council says US centric explanations about gold prices are risky for investors.
US dollar has risen more than 25% against international currencies since summer 2013.
But gains could be short-lived, as rising supplies may weigh on prices again.
US dollar is set to extend its rally against emerging market (EM) currencies over the next 12 months.
North American companies' losses increased by 53% to $27.13bn in 2014.