The deaths of three patients at a psychiatric hospital in Perth are under investigation.

A probe has been launched by the procurator fiscal into the circumstances of three deaths at Murray Royal Hospital between May 22, 2013, and November 4, 2015.

It is thought the deaths were suicides committed while the patients were in care.

Jodie McNab, 22, died in care on May 22, 2013, after being admitted to the Perth hospital nine days previously.

Her mother, Tracy Swan, went on to set up the Lighthouse for Perth charity, which works to provide a place of safety for people suffering from a mental health crisis.

Speaking to STV, Ms Swan said: "Jodie got sectioned through self-harm about nine days before the incident actually happened and she was under constant observation.

"Unfortunately, on May 18, there was an incident where she ended up losing her life. She was on life support for four or five days but there was no hope at the end so we had no choice but to switch the machine off."

"We haven't had any explanation how it got to that stage."

Ms Swan added: "I'm so angry that it happened in hospital because it's supposed to be a safe place ... she should have been safe there.

"If it had happened outwith the hospital I could have maybe accepted it a little bit, but the fact she was in the care of them and under section is beyond all comprehension to me."

Ms Swan wants a fatal accident inquiry to take place into the deaths.

She added she feels NHS Tayside "haven't really learned anything for another two [deaths] to have happened in the same place".

On the Lighthouse for Perth charity she has set up, Ms Swan said: "We do have a lot of good services in Perth, and youth services, but unfortunately they're stretched to the limit and the waiting list can be really quite long."

She added more out-of-hours support was needed for people suffering through a mental health crisis, saying: "People can't afford to wait until the morning - they're now in a crisis situation, it's just too long. So we're hoping to capture the out-of-hours."

A Crown Office and Procurator Fiscal spokesman said: "An investigation into the circumstances of three deaths at Murray Royal Hospital Perth, between May 22, 2013, and November 4, 2015, is currently ongoing. Families will continue to be updated in relation to any developments."

An NHS Tayside spokesman said: "As this is a legal matter it would not be appropriate for us to comment."