As investigations continued into the death of a Chinese man whose cell phone exploded, Chinese authorities claim to have found batteries that could blow up when used in Motorola and Nokia cell phones.

Government regulators in the southern province of Guangdong said this week that they had discovered unsafe Motorola and Nokia mobile phone batteries that could explode under certain conditions, the New York Times, Bloomberg, and the Chicago Tribune reported. Both handset manufacturers have said they are cooperating with the safety investigation, but claimed that the batteries fingered by authorities were unauthorised copycats.

The news adds a turn to the ongoing investigation of the June 19 death of Xiao Jinpeng, a 22-year-old welder who died after the battery in his handset apparently exploded. However, neither Motorola or provincial law enforcement has confirmed that the phone, reported as made by Illinois-based Motorola, was actually a company-branded handset. Details of Xiao's death were first published July 4 by the Lanzhou Morning Post, which in turn quoted the state-run Xinhua News Agency.

A Motorola spokesman downplayed the phone connection. "Preliminary evidence suggests it is highly unlikely that a cell phone caused this accident," Yang Boning, a Beijing press officer for Motorola, told the Morning Post. "We are working with the Chinese authorities to determine and investigate the root cause."

According to the New York Times, Chinese investigators are not sure if any of the dangerous counterfeit cell phone batteries have been exported, or if they were only sold domestically.