Buildings at three NHS trusts in England have failed fire safety tests in the wake of the Grenfell Tower disaster, NHS Improvement has said.
Sheffield Children's NHS Foundation Trust is taking steps to remove cladding from one of its buildings following a negative test result.
NHS Improvement said the building is not used for inpatient accommodation and "measures are being put in place to ensure the safety of the building while the cladding is removed".
Cladding from a building at North Middlesex University Hospitals NHS Trust has also failed the test and is being removed. It does not house any inpatients.
King's College Hospital NHS Foundation Trust in south London announced on Monday cladding at one of its buildings was being taken down following tests.
It is also a building not used by patients.
A spokeswoman for NHS Improvement said: "Patient safety is paramount. There will be no disruptions to patient services or continuity of care."
All NHS trusts and foundation trusts have been asked to carry out urgent fire safety checks following the Grenfell Tower fire.
NHS Improvement said it has identified 38 organisations that require extra support to carry out urgent checks.
All 38 of these "priority one" trusts have started 24-hour fire warden patrols, it said.
Of these trusts, 19 have had a review and no further action is needed at this stage.
A further 11 are not required to take further action at this stage "as the building material sampled is not aluminium composite material (ACM) cladding", NHS Improvement said.
A further five organisations are still awaiting combustibility test results.
The other three have failed the tests and are removing cladding.
In a statement, Sheffield Children's NHS Foundation Trust said: "After sending samples of the cladding on our Stephenson Wing for fire safety testing, we have identified material that we will be removing. We are investigating ways to do this as soon as possible.
"Staff who work in this area are also receiving enhanced fire safety training, and we are working closely with South Yorkshire Fire and Rescue to make sure everything is in place to protect the safety of our patients and staff.
"All fire alarms are fully updated and evacuation procedures in line with best practice.
"We can assure families that the hospital remains a safe place to visit."
It added that the top two storeys of the wing, which are not areas where patients stay, have cladding.
The trust has also requested a visit from South Yorkshire Fire and Rescue Service to check the site and confirm there were no immediate risks.
Yesterday, King's College Hospital NHS Foundation Trust said it removed cladding as a precaution at its Denmark Hill site in south London.
It said: "Following an independent review by specialist fire engineers at Arup, one small non-patient area at Denmark Hill was identified as having potentially flammable cladding.
"The safety of our patients and staff is paramount and therefore as a precautionary measure we immediately removed this cladding in its entirety.
"The affected area is not used by patients and there was no disruption to services while the cladding was removed."
North Middlesex University Hospital NHS Trust said: "We want to reassure, patients, staff and visitors that our main ward areas do not have cladding on their exterior walls and as a result are not affected.
"However, cladding on the main building which includes the main outpatient, day surgery, link corridors and office facilities failed the fire resistance test.
"The parties responsible for the ongoing maintenance of the building and who have been working with us on this matter have been informed of the test result.
"The Trust will work with them over the coming weeks to examine the appropriate actions necessary to address this issue.
"The immediate priority for the Trust has been to ensure the safety of patients, carers, staff and other visitors to the Hospital.
"The Trust was visited by a member of London Fire Brigade last week who inspected a number of areas across the hospital and was satisfied with the steps that the Trust had taken to protect patients and staff.
"Given the results of the subsequent tests on the cladding, the London Fire Brigade will visit the hospital again tomorrow.
"The Trust is confident that it has taken all the appropriate steps to ensure the safety of its patients, staff and other visitors to the Hospital."