The BBC understands that the police were called to Drumragh Care Home in Omagh in July following reports of a resident being tied to a chair.
The person was left bruised and shaken.
Four Seasons Healthcare said the home's manager notified the Western Health and Social Care Trust safeguarding team when a member of staff raised concerns about the conduct of an agency nurse.
As an investigation is under way, it said it would be inappropriate to comment.
"We have an active whistle blowing policy that encourages our staff, the people in our care, their relatives or visiting professionals to raise any concerns they may have about any aspect of care or staff conduct," the group's statement added.
"These are always reported to the authorities as appropriate so they can be independently investigated in a thorough and transparent way."
The police confirmed that one person has been released on bail pending further enquiries.
The care home offers day and round-the-clock care for those with dementia and physical disabilities.
A whistle blower contacted the BBC about the incident.
An agency nurse has been arrested following an alleged assault at a care home in County Tyrone.