A woman has been arrested on suspicion of neglect and fraud as part of a police investigation into the deaths of 12 people living in care homes run by the same company.
She was arrested on Thursday morning and remains in custody, Sussex Police said.
The force, which has been looking at how residents at nine care homes out of 20 run by Sussex Health Care (SHC) were treated, has not released any further information apart from confirming the woman was from West Sussex.
West Sussex County Council stopped placing people at some of the homes run by the firm.
Last week social services staff removed four people from Orchard Lodge, in Warnham near Horsham, which is one of the sites under investigation.
A council spokeswoman said this was following a "further risk assessment" and after the Care Quality Commission (CQC) placed the home in special measures when it was given an inadequate rating in September.
During the unannounced inspection in July, the CQC's report said the safety and leadership at the home was inadequate and the effectiveness and quality of care requires improvement but staff were good at responding to the needs of residents.
The council said it continues to look "in detail" at the services run by the company.
A spokeswoman added: "We cannot comment on any part of the police investigation.
"Our priority has always been, and will remain, the safety and care of people living in care homes."
The council's deputy leader Peter Catchpole, a paid adviser for SHC, left his post as cabinet member for adult social care so there was "no risk of conflict" between his role and his work for the company which he had declared.
He later stood down as deputy leader for "personal reasons", a statement issued by the council said.
Charity Compassion In Care set up a whistleblowers' hotline in the wake of the investigation.
SHC said it would continue to work "openly with the police and county council" during the investigation.
A spokesman added: "We are seriously concerned about the impact the ongoing speculation is having on our residents, relatives and staff.
"We firmly believe that, as an organisation, our care practices and training are of a high standard, and that we continue to provide quality care on a daily basis."
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