One staff member is thought to have contracted the disease with two others separately hit by the virus leaving two people in intensive care.
NHS Lothian will lead the team made up of Scottish Government, Health and Safety and Edinburgh City Council experts who will investigate the compost-related cluster in the region and the separate school cases.
Four gardeners, aged between 62 and 84, have been treated for Legionella longbeachae linked to garden compost, while strains of legionella bacteria have also been found in the water tanks of two schools in the west of Edinburgh.
Two of the four gardeners are still in intensive care at Edinburgh Royal Infirmary and the two others have been discharged, NHS Lothian said.
Cargilfield Preparatory School in Barnton was shut on Friday and is expected to reopen tomorrow. One staff member is awaiting test results for suspected legionella.
Cramond Primary was found to have legionella in its water in a test on Thursday and the system was cleaned overnight.
Parents were emailed and told that following a test of the water supply evidence of legionella was found.
Public health experts will meet on Wednesday when it is expected more informa-tion will be made available on the sources of the comp-ost used by the gardeners and the results of the water tank tests.
A spokesman for the Scottish Government declined to comment further ahead of the meeting.
Simon Northcott, head teacher at Cargilfield, said: "Following routine inspections, potentially contaminated water was located in three places at Cargilfield School.
"The three buildings were closed and the school has been working with the environmental health authorities to minimise any potential health risk."