Its stock came under pressure in February following accusations of aggressive accounting by Iceberg Research, a little known research group, although PwC, the accounting firm, supported the company's financial reporting in August.
Commodities traders, which for years made money shifting metals from mines in Africa and Latin America to manufacturers and smelters in China, have been battling tough trading conditions this year.
Prices for most metals have fallen to their lowest levels in more than five years principally because of China's economic slowdown. Among other things, a weaker renminbi and lower interest rates have reduced demand from Chinese traders for imported metals to use as collateral to obtain loans.
Noble's profit before interest and tax at its metals and mining business fell to $3 million in the first half of this year, down 98 per cent compared with the same period in 2014.
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Noble blamed its poor performance on falling physical premiums: the surcharge customers must pay for immediate delivery of metal at a place of their choosing.
Premiums, which are added to the cost of metal traded on the London Metal Exchange, have slumped this year because of weaker demand for raw materials and a supply glut in several commodities.
Noble is looking to focus its metals and mining business on aluminium and alumina, according to one person close to the company.
The problems in metals trading have impacted several large commodities firms. For example, Glencore said in August that its trading division's earnings fell in the first half of this year due to "tough metals trading conditions, particularly aluminium and nickel affected by the collapse in physical premiums".
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By contrast, oil trading has been resilient this year because a glut of crude created profitable storage and arbitrage opportunities. In the six months to June, Noble's energy business, which includes coal trading as well as oil and gas, reported profit before tax of $363 million, up 36 per cent.
Noble on Thursday announced the hiring of Wael Amer, a former head of oil trading in the Middle East and east Africa at Trafigura, another commodities firm, to help expand the company's energy business.