NEW YORK (REUTERS) - Singapore-listed Noble Group's senior US metals traders Scott Evans and Jeff Romanek have left the company, four sources said on Tuesday (Oct 7), the latest in a string of high-profile departures as Asia's biggest commodity trader battles weak metals and oil prices.

The departures come as Noble seeks to shore up its balance sheet and reduce its exposure to capital-intensive operations like trading copper, and returns to its historic roots in aluminum and alumina.

Both traders were hired as part of the company's recent years-long push into copper, zinc, lead and nickel. Mr Evans joined 2-1/2 years ago from Goldman Sachs and Mr Romanek followed from the Wall Street bank in April last year.

A spokeswoman for Noble declined to comment on the situation. The sources requested anonymity because they are not authorized to speak to the media.

Mining and metals accounted for 20 per cent of the company's US$34 billion revenue in the first half of the year.

Their exits reflect internal ructions as the trader pursues options, including selling core businesses, to boost market confidence after a bruising accounting dispute.

The moves also underscore challenging market conditions for merchants as prices of industrial raw materials languish at six-year lows.

Commodity traders carrying big inventory on behalf of customers have been hit by the unprecedented plunge this year in aluminum premiums AL-PREM, which are paid on top of the benchmark London Metal Exchange prices.

In the second quarter, Noble's metals and mining segment swung to a loss before interest and tax of US$50 million (S$71 million) after an unprecedented drop in aluminum premiums AL-PREM. That compared with a profit of US$102 million in the same period last year.

The group reported net profits of US$62.6 million, compared with US$65.8 million a year earlier.

In its earnings report, it said the copper business performed strongly due to strong customer growth and volumes amid broader copper market weakness. Overall volumes in copper grew 30 per cent year-on-year in the first half.

Noble's rival and the only other listed commodities merchant Glencore has also faced pressure from shareholders to cut costs and reduce debts. The collapse in its shares have sparked worries about the sector's outlook.

Noble's shares have hit record lows this month, while the yield on its bonds has tripled in just over a month to some 18 per cent.