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: "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 inquiries 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.

He added: "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."