Four patients died unexpectedly on a mental health ward which had more than the recommended number of beds on it, a report has found.
The Care Quality Commission (CQC) carried out an inspection into East London NHS Foundation Trust following the deaths on an all-male ward between December 2016 and July last year.
Some wards within the trust continue to have more beds than the Royal College of Psychiatrists' recommended maximum of 16, the report said.
Ash ward, where the deaths occurred, has reduced its beds from 27 to 19, the CQC found, but the health watchdog said the trust should continue to review numbers on acute wards "so they are in line with national guidelines".
The report did not give further details on the deaths other than to say the four incidents were being investigated by the coroner when the inspection took place in November.
Another "near-miss incident" incident related to "serious self-harm" on the all-female Crystal ward, which had 18 beds at the time of the inspection.
The CQC said contraband items on wards were a concern, despite the fact patients were routinely searched after returning to the ward from leave.
The report said: "During the inspection we heard about a blade being found on Crystal ward and plastic bags being found on Jade ward."
The watchdog said there was a concern patients' health may have been put at risk because the appropriate checks were not always made after "rapid tranquilisation" was carried out.
The CQC also said security breaches were not being consistently reported and less than three quarters of staff had taken up basic and immediate life support training.
Recruiting and retaining nursing staff continued to be "problematic", the inspectors found, but the report said initiatives were under way to address this and that staff felt the service was getting better.
Inspectors found improvements had been made in a number of areas including staff receiving training on suicide prevention and managing physical health conditions, better risk assessments and safe management of medicines.
There was also good feedback from patients who reported that staff involved them in care planning and treatment.
Dr Paul Lelliott, Deputy Chief Inspector, said: "It's good to see that the trust has learnt from serious incidents and made some improvements in the quality of care at East London NHS Foundation Trust's acute wards for adults of working age and PICUs (psychiatric intensive care units) in Luton and Bedfordshire.
"However, I would like to see care for patients improve further, when we next inspect this service. I was though pleased to see that patients reported that staff involved them in planning their care and treatment."
The service was not given a rating in this instance, but the trust had been rated overall outstanding after a June 2016 inspection.
East London Foundation Trust provides an acute mental health service for adults in Luton and Bedfordshire.
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