Patients were moved to ward 6A at the Queen Elizabeth University Hospital (QEUH) in Glasgow as a temporary measure in September when two children's cancer wards at the neighbouring Royal Hospital for Children (RHC) were closed for upgrades following an infection outbreak.
Two months later, a 10-year-old boy being treated for cancer at QEUH was one of two patients at the hospital who contracted an infection linked to pigeon droppings and later died.
The deaths led Health Secretary Jeane Freeman to order an independent review into whether the design, build, commissioning and maintenance of the £842 million two-hospital campus, which opened in 2015, has had an adverse impact on the risk of healthcare-associated infection.
Now, three patients have contracted infections at ward 6A in the past fortnight.
Two are from different rare bacteria and an investigation is being carried out into the source of the infections, with none so far being identified.
Greater Glasgow and Clyde Health Board said infection rates at the ward remain within expected levels.
Part of the ward is being kept empty for investigations and new admissions are being temporarily diverted, with antibiotics being given to remaining inpatients as a precaution.
A spokeswoman for the health board said: "A number of measures have been taken to enhance the environment within ward 6A and to improve the quality of the water supply and of the air quality. These measures are having good effect with positive results.
"Infection rates remain within expected levels for the patients treated on ward 6A, however in light of two rarer infections, we are taking the precaution of reviewing infection control practices and procedures and the ward environment.
"These are two different infections and at this stage there is nothing to link the infections to the ward's infection control practices or the environment.
"In order to facilitate our investigations, we require to keep part of the ward unoccupied for a short period.
"New admissions are therefore temporarily being diverted. Outpatients and day cases continue as normal.
"In addition we are taking the precaution of prescribing prophylactic antibiotics for patients on the ward."
She said the patients are receiving treatment for their infection and urged visitors to practise good hand hygiene on visiting the ward.
The children's cancer wards 2A and 2B at the RHC remain closed for an ongoing ventilation system upgrade, with the health board unable to provide an expected end date, after the water and drainage was fixed following infections linked to water-borne bacteria.
A total of 25 cases of infection were found at the children's hospital between 2016 and September 2018.
Following an investigation, which found "widespread contamination of the water system that serves both QEUH and RHC", health watchdog Health Protection Scotland is carrying out a national review of water systems at all healthcare facilities in Scotland built since 2013.
The health board said upgrades to the water system at RHC and QEUH are now complete.