A nursery has been closed after allegations that indecent images were found on a computer linked to the establishment.
West Yorkshire Police have stressed there is no evidence to suggest any children attending the Short Circuits Care Club, on Hollingwood Lane, Bradford, have been harmed and no-one has been arrested.
A police spokesman said: "Following allegations of indecent images being held on a computer linked to an address on Hollingwood Lane, Bradford, police are today interviewing four people.
"The investigation into these allegations is at an early stage but officers would like to stress that, at this current time, we have no evidence to suggest that any children who attend the premises have in any way been harmed.
"All parents of children at the establishment have been notified of the allegations."
He said the four people who are being interviewed are a man and a woman, both in their 40s and from the Bradford area. The other two people are men aged 22 and 25.
He said: "No one has been arrested in connection with the allegations and inquiries into the matter are continuing."
An Ofsted spokeswoman said: "Ofsted is aware of an incident at the Short Circuit Nursery and is working with the local authority and the police to support their investigation. We have taken action to suspend the registration of the setting while the investigation is being carried out."
The centre is on the site of Hollingwood Primary School but is understood to be run entirely separately. It advertises as a day nursery with places for 35 children.