Noble Group shares slumped on Friday after the Asian commodities trader swung to an unexpected quarterly loss due to asset write-downs, and as investors fretted over a research report questioning its accounting methods.
Noble's shares dropped as much as 7 percent, taking the total decline to 19 percent in a rout that has wiped about $1.1 billion from its market value since Feb. 13 on concerns about how the company is valuing its assets in the face of declining commodity prices.
Bonds also sold off initially before clawing back on short-covering. The bonds due 2020 fell to a low of 101.5 today from Thursday's high debt level of 105, before recovering to 102.5/103.
In a report published online on Wednesday, little-known Iceberg Research said Noble had overstated the value of commodities it held by at least $3.8 billion, a charge Noble has rejected. It was the firm's second such report on Noble in February.
Noble, one of Asia's biggest commodity trading groups, said on Thursday that it took total impairments, write-offs and provisions of $438 million on a range of assets and investments in 2014, following its annual year-end review process.
Still, credit managers said the valuation and accounting controversy had no cash-flow implications.
Read MoreNoble shares take second-day drubbing
"Credit investors don't worry about book values or impairments. We care about cash flows, leverage and debt maturities," said Dhiraj Bajaj, Hong Kong-based portfolio manager at Lombard Odier.
Noble is the second major Singapore-listed commodity trader to have its accounting practices challenged by a small research firm. Olam International was hit by a critical report from Muddy Waters in late 2012, which prompted state investor Temasek to take majority control.
Noble CEO Yusuf Alireza said the write-down of $438 million, of which $200 million related to Australia's Yancoal Coal, was not connected to Iceberg's report.
He said the research report was written by a junior employee Noble had fired. In an email to Reuters, Iceberg said the results validated its research and declined to provide details of its team.
Lucror Analytics noted that the report was "reasonably well constructed and is hardly the work of a junior person".
In the first two hours of trade, 61 million shares were traded, double the average full-day trading volume over the last 30 days.