The QEUH campus, which includes the Royal Hospital for Children, is the focus of a public inquiry looking at whether problems with water and ventilation systems were to blame for infections and patient deaths.

Earlier this month, in its closing submission, NHS Greater and Clyde for the first time admitted that some infections among child cancer patients were “on the balance of probabilities” caused by the hospital environment.

COPFS is conducting a separate investigation into the deaths, which could result in the health board which manages the hospital being prosecuted for corporate homicide or under health and safety laws.

In four cases, including that of Milly Main, two unnamed children and 73-year-old Gail Armstrong, police submitted a “standard prosecution report” last May.

That means they have gathered evidence which leads them to suspect a crime has been committed, and it is now up to COPFS to decide how to proceed.

With the three other cases, involving Andrew Slorance, Tony Dynes and Molly Cuddihy, evidence is still being gathered and police have not yet submitted a prosecution report .