Shares in the embattled commodities trader Noble Group jumped as much as 40 percent to S$0.28 on the Singapore Exchange on Monday.
About 7.2 million shares changed hands by afternoon trades compared to a 30-day average of 9 million shares.
The recent surge in share prices prompted the Singapore Exchange to issue a query to the company regarding its trading activity. Noble is yet to respond to the query.
The Hong Kong-based firm last week completed the sale of Noble American oil business to Vitol U.S. Holdings about $580 million.
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Vitol, the world's largest oil trader, closed a deal to buy Singapore-listed Noble's oil liquids unit Noble Americas Corp last year.
Noble has been forced to shrink its business, exiting loss-making and non-core operations in order to survive.
Last year, the company announced the surprise departure of its co-Chief Executive Jeff Frase, just days after it reported a third-quarter loss of $1.17 billion and warned that the operating environment remains challenging.
The trader's market capitalization, which once topped $10 billion, has shrunk to $260 million.
