Apple has promised to "fully investigate" reports that a woman was killed by an electric shock from her iPhone 5 while charging it at home. A spokeswoman for the technology company said: "We are deeply saddened to learn of this tragic incident and offer our condolences to the ... family. We will fully investigate and co-operate with authorities in this matter." According to mainland media reports, Ma Ailun, a 23-year-old flight attendant with China Southern Airlines, was picking up her iPhone 5 to answer a call while the battery was being charged when she was electrocuted and killed. The incident reportedly took place at her home in Xinjiang on Thursday. It has sparked safety concerns over the bestselling smartphone. Ma's brother, Yuelun, said in an interview with Apple Daily that the family believe she was killed by an electric shock while using the phone. He said the iPhone in question and its accessories had been handed over to Xinjiang police for investigation. Online, microblogging site Weibo was flooded with posts urging fellow users not to make calls while charging their phones. Experts in Hong Kong warned against using any electrical device while it is being charged. Johnny Sin Kin-on, a professor at the Hong Kong University of Science and Technology, said: "There is a risk using an electrical device while its installed battery is being charged, be it a shaver or a phone." Dr Peter Chiu Ping-kuen, head of the department of electronic and information engineering at the Hong Kong Institute of Vocational Education (Sha Tin), expressed a similar view. "But we do not know the circumstances of the incident and it is not suitable to jump to any conclusions at this stage," he said.