A police investigation at the hospital where nurse Lucy Letby murdered seven babies and attempted to kill seven others has been expanded to consider whether there was evidence of gross negligence manslaughter.

Cheshire Police said it opened a corporate manslaughter investigation at the Countess of Chester Hospital in October 2023.

Det Supt Paul Hughes said: “As our enquiries have continued, the scope of the investigation has now widened to also include gross negligence manslaughter.”

An undisclosed number of suspects have been notified by the force, he added, before stressing that “no arrests or charges have yet been made”.

The Senior Investigating Officer said: “This is a separate offence to corporate manslaughter and focuses on the grossly negligent action or inaction of individuals.

“It is important to note that this does not impact on the convictions of Lucy Letby for multiple offences of murder and attempted murder.”

Referring to the gross negligence manslaughter investigation, Det Supt Hughes said: “We will not be confirming the number of people involved or their identity.

“Both the corporate manslaughter and gross negligence manslaughter elements of the investigation are continuing and there are no set timescales for these.”

He also said his force was continuing to investigate the deaths and non-fatal collapses of babies at both the Countess of Chester Hospital and the Liverpool Women’s Hospital between 2012 and 2016.

“Our priority is to maintain the integrity of our ongoing investigations and to support the many families who are at the heart of these,” the senior detective said.

Last month an international panel of neonatologists and paediatric specialists claimed Letby was not responsible for attacking babies.

Panel chairman Dr Shoo Lee told a press conference “in all cases death or injury were due to natural causes or just bad medical care”.

The panel’s concerns have been passed to the Criminal Cases Review Commission (CCRC), which investigates potential miscarriages of justice.

Letby’s legal team hopes her case will be referred back to the Court of Appeal.

Letby, originally from Hereford, is serving 15 whole-life sentences for attacking babies at the Countess of Chester Hospital’s neonatal unit between June 2015 and June 2016.

A public inquiry into the events surrounding her crimes will reconvene at Liverpool Town Hall on Monday for closing submissions.

Inquiry chair Lady Justice Thirlwall is expected to publish her findings in the autumn.