Police and management are stressing that the deaths of four children in nine months at Wexham Park Hospital could be a coincidence.
A female member of the nursing staff at the hospital in Slough has been questioned and released on bail in connection with the deaths. The first death is said to have happened in July 2000.
All four children died on the same children's medical ward, number 24, at the main hospital site.
The hospital's chief executive Margaret Edwards said: "It may well just be a statistical cluster but we've taken it very seriously."
Mrs Edwards added that the deaths were "of children who were not at that time expected it to die."
Detective Superintendent Steve Morrison, of Thames Valley Police, said: "A number of people will be interviewed. It is likely it will take weeks if not months to get a clearer picture of what we are doing.
"The parents are concerned to see the truth established and we will do everything possible to support them."