A former China Southern Airlines flight attendant who was electrocuted in her northwest China home last week was reportedly talking on a charging iPhone 5 at the time of her death.

23-year-old Ma Ailun was making wedding arrangements on an iPhone that was plugged into a charger when her family says she received a fatal electric shock.

Ma's sister challenged claims that the iPhone was knock-off, posting on the social networking site Sina Weibo that the device was purchased at an official Apple store last December.

Apple China released a statement over the weekend saying it was "deeply saddened about the accident" and vowed to "thoroughly investigate the accident and collaborate with the police investigation."

"(I) hope that Apple can give us an explanation," Ma's sister wrote on her Weibo account. "I also hope that all of you will refrain from using your mobile devices while charging."

Experts said the phone's 3-to-5 volt output would not have been enough to cause harm on its own, but a problem with the charger could theoretically increase the output to a lethal 220 volts.

The Atlantic Wire has a round-down of other possible explanations, including the fact that Ma had "left the bath to answer the phone."

[photo via AP]