A female healthcare worker in the UK has been arrested on suspicion of the murder of eight babies and the attempted murder of another six newborns.
Last year, Chester Police investigated the neo-natal unit at the Countess of Chester Hospital and Detective Inspector Paul Hughes, who is leading the probe, said when officers first looked into the case, their focus was on the death of 15 babies.
But he said today: "Since the start of our enquiries and, as the information gathering process has continued, the scope of the investigation has now widened.
"We are now currently investigating the deaths of 17 babies and 15 non-fatal collapses between the period of March 2015 and July 2016."
The woman was arrested on Tuesday morning (local time). Police have not said if the arrested woman is a nurse, doctor or other health professional.
DI Hughes added: "This is a highly complex and very sensitive investigation and, as you can appreciate, we need to ensure we do everything we possibly can to try to establish in detail what has led to these baby deaths and collapses.
"Due to the nature of the case and, as part of our ongoing enquiries, we have consulted with a number of medical specialists to ensure that we carry out as thorough an investigation as possible. We have also spoken to a large number of people to gather as much information as we can.
"As a result of our ongoing enquiries we have today arrested a healthcare professional in connection with the investigation. She was arrested earlier this morning on suspicion of murder in relation to eight of the babies and attempted murder in relation to six of the babies and is currently in custody.
"We recognise that this investigation has a huge impact on all of the families, staff, and patients at the hospital as well as members of the public.
"Parents of all the babies are continuing to be kept fully updated and are being supported throughout the process by specially trained officers.
"This is an extremely difficult time for all the families and it is important to remember that, at the heart of this, there are a number of bereaved families seeking answers as to what happened to their children."
The officer added no further details would be available at this stage as the investigation was still ongoing, and said there was no end date in sight.
In a statement, Countess of Chester Hospital medical director Ian Harvey said: "We are continuing to support Cheshire Police with their ongoing investigation.
"Asking the police to look into this was not something we did lightly, but we need to do everything we can to understand what has happened here and get the answers we and the families so desperately want.
"The Countess is now equivalent to a Level 1 Special Care Baby Unit and we are confident the unit is safe to continue in its current form."