Assistant County Medical Examiner for Collin County, also revealed there were no alcohol or drugs in Lucy's system at the time.
Lucy's mum and boyfriend yesterday paid tribute to the former Manchester Metropolitan University student.
It is understood Lucy had travelled to the US with her boyfriend just after Christmas for a family holiday.
"She was the embodiment of wonderful contradictions - she adored travel and being away, experiencing new places and cultures, yet at the same time, she loved nothing more than snuggling up in her pyjamas with her candles on at home.
Lucy Harrison, 23, was discovered at the property in Texas on January 10.
