Sian O'Callaghan is likely to have died from head injuries, a coroner heard as an inquest into her death was opened and adjourned in Oxford.

The 22-year-old personal assistant from Swindon went missing from the town's Suju nightclub on March 19. Her body was found near the Uffington White Horse last week.

A Home Office forensic pathologist is still working to confirm a precise cause of death while Wiltshire Police continue to examine the remains of a second woman discovered near Eastleach, on the boundary of Oxfordshire and Gloucestershire.

Detective Superintendent Steve Fulcher confirmed that Miss O'Callaghan's death was formally certified last Thursday, following the arrest of taxi driver Christopher Halliwell, who has subsequently appeared in court charged with her murder.

Coroner Nicholas Gardiner, sitting at Oxford Coroner's Court, said examinations were ongoing to determine exactly how the young woman died: "I think the actual cause of death has not yet been defined but is likely to be head injuries of some description."

Miss O'Callaghan was formally identified by Pete Shawe, the partner of her mother Elaine, who had known her for four years.

Today's ten-minute hearing came after Mrs O'Callaghan described news of her daughter's death as "the worst of the worst" she could imagine.

"I always had hope but I still tried to prepare myself for the worst," she told the Swindon Advertiser newspaper. "It was the worst of the worst that I could've imagined. But they'd found her. It was a relief in a way. I would have hated to live the rest of my life looking over my shoulder and looking at every brunette girl, wondering if it was her."

Miss O'Callaghan had been out with friends before she disappeared in the early hours of March 19. She was last seen alive in CCTV footage filmed close to the Suju nightclub, only half a mile from the flat she shared with her boyfriend, Kevin Reape, 25.

On Wednesday, Halliwell, 47, appeared at Bristol Crown Court accused of her murder.