Tang Jun was only person from the company helping the investigation and the issue being probed remained unknown, a spokesman for Suntech's parent Shunfeng International Clean Energy (SFCE) told AFP today, adding the firm's operations were "all normal".
Tang is the latest senior Chinese businessman to drop out of circulation for unclear reasons.
In January one of China's most prominent clothing firms, Metersbonwe, announced its chairman Zhou Chengjian had returned to work, a week after saying he had disappeared amid speculation he had been caught up in an insider trading investigation.
Suntech Power was once the world's largest solar panel producer, at a time when Chinese manufacturers were flooding the global market with cheap products, causing trade disputes with the EU and US.
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The firm collapsed in 2013 after it announced its main Chinese unit Wuxi Suntech would seek bankruptcy and restructuring, resulting in a bond default in the US worth over half a billion dollars.
The company later said it would receive a USD 150 million local government bailout and it was eventually bought by Hong Kong-listed Shunfeng for 3.0 billion yuan (now USD 462 million).
SFCE shares were down 1.32 per cent in Hong Kong by the break.