Police and Ofsted, the body which oversees nurseries, said they had launched a joint probe last month into the Rocking Horse Nursery in the village of Plumtree after a child was taken to hospital after suffering an unexplained fracture.
“Subsequent enquiries have so far established that two further children who attended the Rocking Horse Nursery had also suffered unexplained fractures this year,” a Nottinghamshire Police spokesman said.
“All the children involved are aged between one and two years, and officers have questioned five people in connection with the investigation.
“Two of those were arrested and subsequently released on police bail, while the remaining three were questioned under police caution.”
Police said there was no suggestion of any sexual abuse at the nursery which has places for 90 children aged up to four.
The nursery has now been closed.
“While the investigation is ongoing, we have taken immediate steps to ensure the safety of children by suspending the provider’s registration,” an Ofsted spokesman said.
“This means that the nursery is closed until further notice.”
The nursery said it could make no comment while the probe was ongoing.