The Procurator-Fiscal is investigating after three people undergoing treatment at Murray Royal Hospital, in Perth, died.
It is understood that all the deaths involved the suicide of patients being treated in the secure Moredun ward.
Jodie McNab spent five days on life support prior to her death on 22 May, 2013. The 22-year-old had been admitted to Murray Royal nine days before she died.
Her mother, Tracy Swan, set up the Lighthouse for Perth charity to help those with mental health issues in the wake of her loss. She hopes she will finally get the answers she seeks in relation to Jodie’s death.
“It shouldn’t have happened,” she said. “I put her in there because it was a place of safety and it wasn’t in the end.
“I’m not happy with where we are at right now and I am looking for answers. Going by my experience with them and my daughter
“I believe there’s a lot of questions needing answered. Obviously they haven’t learned after Jodie’s death for there to be another two afterwards.”
She said she hoped that the investigation would lead to a fatal accident inquiry.
“Getting the answers would help me,” she said. “I really hope the investigation means that this won’t happen to another family, because it’s the worst possible thing that could happen to any family.
“You put them in there to be safe and for something to happen is beyond all comprehension.”
Mrs Swan lives with her husband, Tommy, in a house that overlooks the grounds of the hospital, which they bought just a few weeks before Jodie was admitted.
She said: “Now we look onto the part of the hospital where Jodie died.
“Sometimes it’s a comfort because you feel she was just there but the majority of times you see the building and you just get so angry.
“If we’d known Jodie was going to end up there and this was going to be the result, we would never have moved here.”
A spokesman for the Crown Office and Procurator-Fiscal Service confirmed that they had launched an investigation, but declined to confirm the nature of the deaths.
An NHS Tayside spokeswoman said: “As this is a legal matter, it would not be appropriate for us to comment.”