Three members of care home staff have been arrested amid allegations of mistreatment and neglect of elderly residents.
One staff member was arrested on suspicion of wounding, one of assault, and one of neglecting a patient at Briarwood Rest Home in Lostock Hall, near Preston.
Lancashire County Council bosses said they have taken the “unprecedented step” of putting in their own staff to help run the home.
Police said the arrests are part of a continuing investigation into allegations made about the treatment of residents.
Following the initial complaint, other allegations have been made and these are now also under investigation.
A 63-year-old man was arrested on Monday on suspicion of being a guardian neglecting a patient.
He has been bailed pending further enquiries.
A 58-year-old woman from Preston was arrested on June 7 on suspicion of assault and has also been bailed and a 41-year-old woman from Preston was arrested on suspicion of wounding on June 12 and has been bailed.
The care home in Todd Lane South provides accommodation for those over 65 years old who require nursing or personal care.
The health watchdog, the Care Quality Commission, said the home was also being investigated by the local authority safeguarding team.
It also said it recently inspected the home and a report would be published soon.
Detective Inspector Jes Holland, of Lancashire Police said: “These arrests are part of a thorough investigation into serious allegations of mistreatment of residents at Briarwood Rest Home.
“The enquiry is complicated and is at a relatively early stage.
“We have a team of specialist detectives working on this case who are also offering support to those families who may have had loved ones identified as being allegedly mistreated.
“Our priority from the outset has been to ensure the safety of patients within the home and the Constabulary has been working closely with the Care Quality Commission and the Adult Social Care Service at Lancashire County Council.”
Debbie Westhead, CQC’s deputy chief inspector of adult social care in the north, added: “CQC is aware of the arrests of three members of staff and can confirm that this is currently subject to investigation by the police and local authority safeguarding team.
“It would be inappropriate for us to comment during the course of their investigations, however, we are in close liaison with all involved agencies and continue to monitor this provider to ensure the safety and well-being of the people living at Briarwood Rest Home.
“We carried out our most recent inspection of the home earlier this month and the findings of this inspection will be published soon.”
Mike Banks, Lancashire County Council’s director of commissioning, said: “As the local safeguarding authority, we are supporting the police with their investigation into the alleged mistreatment of a number of residents at Briarwood Rest Home in Lostock Hall, near Preston.
“We have also taken the unprecedented step of temporarily putting our own staff in to help run the home, alongside the existing staff, until the owners have confirmed their plans for the future.
“Together with the police, we have held a meeting with the residents’ families to bring them up to date, and we are continuing to try to contact a small number of relatives who have not responded so far.
“In the meantime, we have allocated a social worker for every resident at Briarwood and will continue to work closely with our colleagues in the NHS and Care Quality Commission to make sure everyone in the home is safe and well looked after.”