A female healthcare worker is under arrest on suspicion of the murder of eight babies and the attempted murder of another six babies after an investigation of the neo-natal unit at the Countess of Chester Hospital, Cheshire Police said.
The arrest comes as part of a long-running police investigation following a high number of baby deaths at the hospital, initially between June 2015 and June 2016.
Police say the investigation has since widened and they are now looking into the deaths of 17 babies and 15 non-fatal collapses between the period of March 2015 and July 2016.
Police have not said if the arrested woman is a nurse, doctor or other health professional.
Detective Inspector Paul Hughes, who is in charge of the investigation, said: "The investigation into the neonatal unit at The Countess of Chester Hospital is continuing. Since it was first launched in May 2017, a dedicated team of detectives have been working tirelessly on this case.
"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.
"When the investigation was first launched it was focusing on the deaths of 15 babies that occurred between the period of June 2015 and June 2016.
"In addition the investigation was also conducting a review of six non-fatal collapses during the same period.
"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.
"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.
"Whilst this is a significant step forward in our enquiries it is important to remember that the investigation is very much active and ongoing at this stage. There are no set timescales for this coming to a conclusion but we remain committed to carrying out a thorough investigation as soon as possible.
"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.
"At this stage we are unable to go into any further details about the investigation but as soon as we are able to provide any further updates we will do.
"If anyone has any information that they want to pass onto the investigation team they are encouraged to get in touch via the Operation Hummingbird mailbox at email@example.com
"Information can also be passed on anonymously, via Crimestoppers, on 0800 555 11 or by calling 101."
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."