Hospital staff are now being interviewed by police as bosses enhance security in the wake of a high-profile saline scare.

It is now a month since workers at Carlisle's Cumberland Infirmary noticed that a small number of saline bags appeared to have been tampered with.

Police were called in by North Cumbria University Hospitals NHS Trust, while fluids were taken out of circulation and security tightened.

Nursing director Maurya Cushlow has now issued an update to staff about the investigation and reiterated new security measures.

"As part of the ongoing investigation, Cumbria Constabulary has started to interview members of staff," she said.

"I thought it would be timely to reinforce some of the security measures we must all be adhering to for the protection of staff as well as patients.

"These security measures are permanent so it is important we all get used to new ways of working."

She went on to explain some of the key measures that staff across the Carlisle and Whitehaven hospitals must now adhere to.

This includes having two people thoroughly checking IV fluids before use, looking for even the slightest signs of damage.

Anyone with concerns must immediately raise them with a senior member of staff, who will then take action.

Drug room access has also been tightened.

"Only authorised members of nursing and pharmacy staff may enter the room and the access code must not be shared inappropriately.

"All members of staff who enter the room must complete the sign-in and sign-out sheet without exception. Any breaches of protocol should be formally reported as an incident," added Ms Cushlow.

Staff are also reminded that doors should never be wedged open or left on a latch. Swipe cards must be used to access non-public areas.

She adds: "Please continue to ensure you are vigilant as to who is coming into your ward or department as a matter of routine.

"If somebody has entered your ward or department by following a member of staff through the door, ask the person who they are and for identification where appropriate.

"It is the responsibility of each and every one of us as members of staff to be vigilant and challenge appropriately."

No further information about the police investigation has been released to date. An incident room has been set up and a team of detectives - led by Cumbria's top detective Andrew Slattery - are working on the case.