Letby has been on bail since her arrest last year and it is understood her home is being searched by police.
According to The Telegraph, the hospital first launched an internal inquiry after finding that premature babies who had collapsed with heart and lung failure were unusually impossible to resuscitate. They also developed strange blotches on their arms and legs after death.
A spokesperson for the Countess of Chester Hospital confirmed the hospital was 'co-operating fully' with the investigation.
'We fully appreciate that it continues to have a big impact on all those involved - including the families of the babies, staff and patients at the hospital as well as members of the public,' Detective Inspector Paul Hughes said.
'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.'
