Chinese lender says Dame Jenny notified it that she had served as chairman and independent director of the collapsed group.
The government expects to provide $2b of the extra cost, Prime Minister John Key says.
"There is no way any assessor could pinpoint the final cost until restoration is well under way."
Proposed project tipped as Queensland's biggest tourism infrastructure development in the state's history.
The Christchurch-based unit of American firm Ceres Environmental Services says it has a "strong interest" in buying Mainzeal Property and Construction.
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