SINGAPORE (REUTERS) - Singapore-listed Noble Group overstated the value of commodities it holds by at least US$3.8 billion (S$5.15 billion), Iceberg Research said in a report on the Asian commodity trading firm's accounting practices.

"Impairing these fair values dramatically impacts Noble's performance indicators," the little-known research firm said on its website on Wednesday, its second report this month raising questions about Noble's books.

Trading in the company's shares was halted on Thursday morning pending an announcement. Noble is set to report its results later in the day.

Iceberg released its first analysis on Feb 15, to which Noble issued a detailed rebuttal.

The company's shares fell a combined 13 per cent in the two trading sessions following the initial report. It has recovered about 1 per cent since then.

Noble did not have an immediate comment on the fresh report.

Iceberg Research has in the past declined to comment on its background, analysts and methodology.