The allegation of voyeurism is understood to relate to a girl aged 16 and police have said at this stage there is no evidence that any of the images relate to children who have been in his care.
Hoffman is understood to have been employed by the same company for more than a decade working at more than one centre.
The parent of one child who attends one of the nurseries expressed her concern about the situation last night.
She said: "All the parents are so worried, we don't know what is going on."
A statement issued on behalf of the Jancett Group said: "The nursery owners have been informed by police that there are no images at this time of any child that attends or has attended any nursery or child care setting operated by the Jancett Group."
It went on: "On Wednesday, May 23, a member of staff discovered a recording device in a staff lavatory. The police were immediately contacted by the nursery and requested to attend.
"Officers duly attended the nursery and removed the device. In the course of an internal investigation having commenced immediately by the nursery owners, police were notified during Thursday May 24 as to the identity of a male member of staff who was arrested by police later that day."
Two nurseries, where Mr Hoffman is understood to have worked were closed and searched by police, but reopened on Monday.
The company's statement continued: "The owners and all staff at the nurseries will continue to co-operate fully with and assist the police and any partner agency in the continuing investigation."
It said Jancett management "have continued to keep parents, staff and students informed and will continue to consult with parents, staff and students and offer any assistance required".