Those requesting to be designated as a core participant include Hastings District Council, Hawke's Bay Regional Council, Hawke's Bay District Health Board, Local Government New Zealand, and Water New Zealand.
MWH New Zealand Ltd, which has a services agreement with the district council, also requested to be designated as a core participant.
Also to be discussed today is whether to conduct the inquiry in two stages.
Stage 1 would cover the cause(s) of the outbreak, whether any person or organisation was at fault, the adequacy of drinking water supply management for Havelock North, and the preparedness and responses of local and central government agencies and any other relevant parties.
Stage 2 would cover systemic matters and possible changes needed for the future.
The inquiry panel is chaired by Honourable Lyn Stevens QC, who is joined by NZQA CEO and former director-general of health Dr Karen Poutasi CNZM, and local government and engineering expert Anthony Wilson.