The mother of Libby Squire, the University of Hull student whose death is being treated as a potential murder after her body was recovered from the Humber estuary last Wednesday, said she had lost one of the most precious things in her life.

Lisa Squire said in a Facebook post: “I kept you safe as long as I could,” and told her daughter she was sorry that she could not protect her on the night she died.

“My baby girl is gone. Gone for ever. No more birthdays with us. No more Christmas Days with us. No more family time all together,” she wrote.

Calling her daughter by her pet name, Pie, she said: “I have lost one of the four most precious things in my life. I cannot thank you enough my darling Pie for making me a mummy. For choosing me to be your mummy. It’s an honour, a privilege and a joy.

“I kept you safe for as long as I could and I am so sorry I could not keep you safe on that night. I’m sorry. I’m so, so sorry. I love you my beautiful girl with all my being and I always will. Until we meet again, my Pie. I love you more.”

She added: “There have been so many low points but by far the worst point was having to call [Libby’s boyfriend] Connor, the absolute love of her life, and tell him: ‘I am so sorry, the girl you love the most in the world has gone.’

Detectives have said they are treating Libby’s death as a potential homicide but said they will not be releasing the results of a postmortem examination for investigative reasons.

The philosophy student’s disappearance on 1 February triggered a huge search operation involving more than a hundred officers and a large team of volunteers.

During the investigation into her disappearance, 24-year-old Pawel Relowicz, of Hull, was arrested on suspicion of abduction.

He has since been remanded in custody having appeared in court on a number of charges unrelated to Libby’s death and disappearance of burglary, voyeurism, outraging public decency and receiving stolen goods.