The sister of victim Ma Ailun posted on Sina Weibo, China's equivalent of Twitter, Ma was killed Saturday as she tried to answer a call while her iPhone was charging at her home in Changji, China's state-run news agency Xinhua reported Sunday.
"[I] hope that Apple Inc. can give us an explanation. I also hope that all of you will refrain from using your mobile devices while charging," read the post that has gone viral.
Apple, based in Cupertino, Calif., announced Sunday it would "thoroughly investigate" the incident.
Ma's father, Ma Guanghui, said his daughter's body showed signs of electrocution.
Local officials confirmed Ma died of electrocution, but haven't verified whether her iPhone was involved.
"We are deeply saddened to learn of this tragic incident and offer our condolences. ... We will fully investigate and co-operate with authorities in this matter," an Apple spokeswoman said.
Ma's sister said Ma bought the iPhone in December at an official Apple store and was using the original charger to recharge the phone when the incident occurred.
Experts told Xinhua cellphones put out three volts to five volts, which isn't enough to harm the human body. They said people experience an electric shock at about 36 volts.
"However, if the charger or the circuit has a problem, such as a broken wire, it can lead to a shock of 220 volts," a high school physics teacher was quoted as saying in a media report.