An outbreak of Legionnaires' disease which saw two deaths and 22 people infected has been officially declared over.
An 85-year-old man and Bev Morgan, 49, of Rhymney, Caerphilly county, both died in cases linked to the outbreak in the Heads of the Valleys area.
The investigating team has announced its findings ahead of a report.
No new cases of the disease have been identified since the last person fell ill on 10 September.
Dr Gwen Lowe, of Public Health Wales and chair of the outbreak control team, said: "We have not seen any new cases of Legionnaires' disease linked to the outbreak area for more than a month and we have extensively investigated all possible links between the 22 cases linked to the outbreak area.
"Both our microbiological and epidemiological investigations indicate that there are a number of potential sources for these 22 cases.
"All plausible sources have been fully investigated and precautionary action taken and advice given where indicated. This has involved local authorities from all over south-east Wales."
The outbreak control team, comprising Public Health Wales, the Health and Safety Executive (HSE) and environmental health officers from eight south Wales local authorities, will be producing a report on the outbreak.
The outbreak area involved a corridor 12km (7.5 miles) either side of the Heads of the Valleys Road (A465) between Abergavenny and Llandarcy. People were linked to the outbreak if they lived in, or visited, this area in the two weeks before they fell ill.
All 22 cases required hospital treatment.
Ten further people with the disease were investigated to see if they were linked to the outbreak but were later discounted.
Two of these patients died - a 70-year-old man and a 64-year-old woman.
The HSE has inspected all registered cooling towers and evaporative condensers in the Merthyr Tydfil, Blaenau Gwent, Rhondda Cynon Taf and Rhymney areas - 28 in total.
Four industrial sites in Merthyr Tydfil, Rhymney Valley and Cynon Valley were closed but none were confirmed as the source. They are all now back in operation.
HSE and council environmental health officers also visited more than 100 other workplaces.
Public Health Wales said their investigations had identified two distinct clusters - six people with Legionnaires' linked to a small geographical area in Rhymney, and six people with Legionnaires' spread out across a wider area in the Cynon Valley.
Dr Lowe added: "Growing legionella bacteria is very difficult and has not been possible in samples from many of the cases.
"Microbiological results from the seven human samples that have been grown show that every one is genetically distinct, suggesting a different source of infection for each of these seven cases.
"We have not been able to obtain samples for most of the cases in the two main clusters.
"This strengthens our suspicions that we are dealing with several different unlinked clusters and cases and is why we have not identified any outbreak strain of legionella for any cluster.
"For the whole outbreak area, plausible sources have been systematically inspected and where indicated, sampled.
"Cooling towers from industrial processes are classically linked to the type of legionella outbreaks where cases are closely clustered in time and place, as is the case with our two main clusters.
"However, the outbreak control team has considered, sampled and ruled out a number of other plausible sources for these clusters."
She added that it had been an extremely complex investigation and a detailed report of the outbreak would be prepared and published in due course.