HANOI • Most of us have probably dozed off while charging our mobile phones at night.

But the seemingly harmless act cost a Vietnamese teenager her life.

According to British news reports, 14-year-old schoolgirl Le Thi Xoan died after being electrocuted by a broken charging cable in her sleep.

Preliminary findings showed that the victim was believed to have plugged her iPhone 6 in to charge and lay on her bed beside it, a practice she did regularly.

The teenager is believed to have come into contact with the broken charging cable, the reports said.

Hanoi police said they found the burnt cable on her bed, with a tear in the rubber casing exposing live wires.

Tape was also found wrapped around the damaged portion of the cable.

The teenager was found unconscious by her parents and taken to hospital where she died, British news site Metro reported.

Doctors confirmed the cause of death as electrocution.

It was unclear if the damaged cable was an original Apple accessory or a third-party product. Police noted that it appeared to be shorter than Apple's original 0.5m-long cable.

According to a Facebook page set up in remembrance of her, she lived in Huong Son, a district in the northern central Ha Tinh province.

Her friends and family wrote tributes to her on the page, saying they loved her and missed her very much.

Investigations are under way.