Detective Inspector Paul Hughes, who is in charge of the investigation, said: "In July 2018 a healthcare professional was arrested on suspicion of murder in relation to the deaths of eight babies and the attempted murder of six babies at the neonatal unit at The Countess of Chester Hospital
. She was subsequently bailed pending further enquiries.
It comes after a spokeswoman for the Countess of Chester Hospital
NHS Foundation Trust said it would not comment until it received formal notice that there had been a change of circumstances.
About 20% of the Countess of Chester Hospital
's patients are estimated to live in Wales and it had been claimed the trust was not being paid for all its work in relation to them.
Detective Inspector Paul Hughes, who is in charge of the investigation, said: "The investigation into the neonatal unit at The Countess of Chester Hospital
"He was taken to the Countess of Chester hospital
but sadly died a short time later."
The teen suffered 'serious injuries' as a result of the incident, and was treated at the Countess of Chester Hospital
Betsi Cadwaladr University Health Board (BCUHB) and the Countess of Chester Hospital
NHS Foundation Trust signed a contract, confirming that normal services have resumed for patients in north east Wales.
Brothers Alex, nine, and James, 11, who kindly agreed for the mini Tesla Model S to be donated to the Countess of Chester Hospital
The chairman of the Countess of Chester Hospital
, Sir Duncan Nichol has said it is "hard to countenance" to treat Welsh patients when it costs "up to [pounds sterling]4m each year".
Cheshire Constabulary has launched the investigation following "a greater number of baby deaths and collapses" at the Countess of Chester Hospital
between June 2015 and June 2016.
Wirral University Hospital NHS Foundation Trust, which runs Arrowe Park and Clatterbridge, says in its 2015/16 annual report: "The Trust will explore with Countess of Chester Hospital
the potential for the development of a single acute general hospital covering Wirral and west Cheshire within the next 10-15 years." The report says there are "clinical and financial benefits" to come from working more closely with the Countess of Chester.