Three key documents about the beleaguered Dunedin Hospital building project have yet to be released.
Dunedin's mayor and locals have questioned the government's assertion the cost could blow out to $3 billion, calling it a "smokescreen".
Ministers put out a report done in May by an Australian expert, that said the approved budget of $1.88b is probably not sufficient.
However, the Rust report also said: "Over the next few months the project will (or at least should) receive three key cost-related deliverables which will provide greater cost certainty."
These three reports comprise a new quantity surveyor's estimate by June, a contractor's target total cost in July and a risk assessment by August.
The report recommended to delay signing up for the second phase inpatients block along the lines of the detailed design, while the cost estimates were updated.
Health Minister Shane Reti's office confirmed on Monday the three reports had not been released.
RNZ could ask for them under the Official Information Act, and it was hoped they might be proactively released soon, his office said.
Mayor Jules Radich has accused the government of adding in "extra costs" that were out of scope, such as car parks and refurbishing the old clinical services block and ward block.
However, the Rust report shows Cabinet was told in March that some things had been left out that were nonetheless "important to project completion", including the car park (a cost is blanked out) and work on refurbishing or demolition, which might cost $325 million, though uncertainty is rife, with the report stating the estimates "should be treated with a high degree of caution".
The $1.88b construction budget does not included an approved $225m for new data and digital services, even though these are integral to any hospital.
Added together, the build budget comes to $2.1b.