US electronic giant Apple Inc. is investigating reports in China that a woman was killed by an electric shock when she took a call on her iPhone 5 while it was plugged.

Ma Ailun, 23, a flight attendant with China Southern Airlines, reportedly died after being electrocuted when she answered a call on the charging mobile phone, the official Xinhua news agency quoted police as saying on Sunday.

Authorities have yet to identify a cause.

Apple said in a statement it was probing the woman’s death but declined to clarify whether this was an isolated case, Reuters reports.

“We are deeply saddened to learn of this tragic incident and offer our condolences to the Ma family. We will fully investigate and cooperate with authorities in this matter,” the statement read.

Ma collapsed and died after using her charging iPhone 5, her sister said on her Weibo account. She urged other users of the device to be careful in a message that went viral online.

Meanwhile, Ma’s father said that his daughter’s body showed signs of electrocution, CNN reports.

The incident is the latest scandal that has embroiled Apple in its second-biggest market. In April, Apple apologized to Chinese consumers and altered iPhone warranty policies after week-long protests.