A female healthcare worker is under arrest on suspicion of the murder of eight babies after an investigation of the neonatal unit at the Countess of Chester Hospital, Cheshire Police said.
The woman is also being held over the attempted murder of another six babies.
Police are currently searching an address in Chester as part of the investigation.
Around a mile away from the hospital a huge police presence was at a house on Westbourne Road in the city. Neighbours said a woman lived at the address, moving in around two years ago.
A blue police tent has been put up in the front garden of the neat semi-detached house, with forensics vans and other police vehicles stationed outside as officers come and go from the property.
The arrest of the woman 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.
Since it was first launched in May 2017, a dedicated team of detectives have been working on the case.
Detective Inspector Paul Hughes, who is in charge of the investigation, said in a statement: “The investigation into the neonatal unit at The Countess of Chester Hospital is continuing.
“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.”
Hughes confirmed the force was investigating the deaths 17 babes and 15 non-fatal collapses.
“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,” he said.
“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.
Anyone with any information should pass it on to 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.