Enquiries are still ongoing into the deaths of eight babies at the Countess of Chester Hospital.
Cheshire police say it is 'too early to say' how long the investigation will take, as it is still in its early stages.
The hospital contacted police after an independent clinical review into neonatal services revealed a greater number of baby deaths and collapses than 'normally expected' during a year-long period from June 2015-June 2016.
Cheshire Constabulary launched an investigation which will focus on the deaths of eight babies between that time period, where medical practitioners expressed concern.
They are also reviewing seven further baby deaths and six non-fatal collapses that occurred during the same period.
In a statement, the Countess of Chester Hospital said they were keen to understand that everything possible has been done to help determine the causes of death in the neonatal unit during that time.
They also said 24 recommendations for improvement highlighted in the review are now underway.
A Cheshire police spokesperson told The Chronicle: "The investigation is currently in the early stages and enquiries are ongoing. At this stage it's too early to say how long the investigation will take."