Police are continuing to search the home of a nurse arrested on suspicion of the murder of eight babies and the attempted murder of six others.
Officers are said to have arrived at the home of Lucy Letby, 28, early on Tuesday, hours before police announced a female healthcare professional had been arrested in a probe into the deaths of 17 infants at the Countess of Chester Hospital.
The arrest comes as part of a long-running investigation by Cheshire Constabulary following a high number of baby deaths at the hospital's neonatal unit.
Police are said to have arrived at Ms Letby's home at around 6am, while officers were also seen at her parents' property in Hereford later on Tuesday.
On Wednesday, a blue tent erected by police remained outside the front of Letby's semi-detached property in Westbourne Road, Blacon, Chester, with a uniformed officer stationed nearby.
Detectives launched an investigation into infant deaths at the hospital in May last year, initially looking at the deaths of 15 babies between June 2015 and June 2016.
On Tuesday police said the probe had widened to include 17 deaths and 15 non-fatal collapses of babies between March 2015 and July 2016.
Detective Inspector Paul Hughes said the arrest was a "significant step forward" in what was a "highly complex and very sensitive investigation".
He added that the probe was "very much active and ongoing" and that parents of all the babies were being updated on the inquiry and supported by trained officers.
Police did not confirm the identity of the arrested health worker.
The Countess of Chester Hospital carried out a number of independent expert medical reviews into the deaths before calling in police.
Medical director Ian Harvey said officials were continuing to support officers with their investigation.
He said: "Asking the police to look into this was not something we did lightly, but we need to do everything we can to understand what has happened here and get the answers we and the families so desperately want."
Mr Harvey added that the hospital is "confident the unit is safe to continue in its current form".
A report published in July 2016 by the Royal College of Paediatrics and Child Health (RCPCH) found significant gaps in medical and nursing rotas and insufficient staffing for the provision of longer-term, high-dependency and some intensive care.
The RCPCH report said paediatric consultants had been concerned since June 2015 about a higher than usual number of deaths on the ward, several of which were "unexplained" or "unexpected".
In a 2013 interview with the Chester and District Standard, Letby said she cared for babies requiring various levels of support.
She had worked at the unit as a student nurse during three years of training before qualifying as a children's nurse at the University of Chester in 2011.
She said she starting working at the unit after graduating.