The allegations relate to the alleged mistreatment and neglect of patients on the stroke unit in November.
Four more people have been arrested by police in connection with allegations of mistreatment and neglect at Blackpool Victoria Hospital.
In November police were contacted by Blackpool Teaching Hospitals NHS Foundation Trust after concerns were raised about the care provided to some patients.
Four healthcare professionals – one man and three women – have today been arrested on suspicion of administering any poison or noxious thing with the intent to injure and ill treatment or wilful neglect.
They're all are currently in custody.
It brings the total number of people arrested to seven after a woman was arrested in November and a man and woman were arrested in December as part of this investigation.
The three individuals – all healthcare professionals – were also arrested on suspicion of administering any poison or noxious thing with the intent to injure and ill treatment or wilful neglect.
They have since been released under investigation pending further enquiries.
These three individuals were suspended in November as part of safeguarding procedures, while the remaining four individuals have been suspended since December following further investigation by police.
A number of post-mortem examinations have been conducted as part of police enquiries.
In January detectives confirmed a murder investigation was on-going following the death of a woman in her 70s on the stroke unit in November.
This is being treated as a separate investigation.
Det Chief Insp Jill Johnston, of Lancashire Police said:
“Our investigation into allegations of mistreatment and neglect of patients at Blackpool Victoria Hospital is very much on-going.
“I understand further arrests could be concerning but I would like to reassure people we have a dedicated team of detectives working on this investigation.
“Our priority and the priority of Blackpool Teaching Hospitals NHS Foundation Trust is to ensure the safety of patients."