The Health Ministry is refusing to say how large the cost overruns are at one of the country's most expensive hospital projects in Christchurch.
The acute services building is months behind schedule.
The budget stood at $463 million but "at this stage", the final cost was "commercially sensitive", the Ministry said. The project was costed at $445m two years ago.
Officials also would not reveal the cost at the outpatients building, which had been originally costed at $72m but has also been delayed.
"Construction on the Outpatients Building was delayed three months while we secured suitable quality steel for the site," the Ministry said in a statement.
"At tender time the contractor anticipated the steel columns would be available from Australasia, but this proved not to be the case. Instead, steel was procured from Asia but with significant quality assurance protocols insisted on by the Ministry of Health. This caused the delay."
It said it had no issues with any of the steel used in the Christchurch Hospital rebuild.
The Ministry blamed the acute services building delays on how complex it was and shortages of skilled labour.
Project documents showed that subcontractors being forced to go back and redo substandard work was also slowing it down.
The acute services building is now due for handover in mid-2019, while the outpatients is scheduled to be handed over this November.