According to the official Xinhua news agency, Ma Ailun was using a third-party charger with her iPhone 4, rather than an Apple-manufactured one. WHen she answered the call, the device was still charging.
Xiang Ligang, a phone expert interviewed by CCTV earlier this week (Google translation), suggested that the manufacturer of the clone charger may cut corners on safety features that should be built into the hardware.
The incident is still being investigated by both local authorities and Apple. It was originally believed to involve Apple's latest model, the iPhone 5, but CCTV said the iPhone in question was Apple's iPhone 4, two generations out of date.
Reports of burns from smoking or exploding batteries are rare, but not that unusual. Occasionally, companies had been forced to engage in massive recalls to correct issues. An electrocution, on the other hand, is something else, entirely.