A new possible opening date for Auckland’s Waterview Connection remains a mystery, with the information redacted in documents released to 1 NEWS.
The documents provide new information about the problems that have affected the $1.4 billion project.
The twin 2.4 kilometre-long tunnels were due to open in April.
But, on March 24 the NZ Transport Agency pushed back the date to "within the next two to three months".
The organisation cited intermittent faults in safety systems which are used to respond to emergencies such as fires in the tunnels.
Internal documents released under the Official Information Act show staff became aware of the issues in the middle of March, during commissioning tests to ensure the tunnels were ready for vehicles.
A memo on March 15 shows officials had planned to open the tunnels over Easter Weekend, but says that "will not be achieved".
The document mentions a new earliest possible opening date but that information was redacted before being sent to 1 NEWS.
The memo says rubber diaphragms in 176 "deluge valves" required replacement after they became damaged during testing.
"It was later identified that the test pressure advised by the manufacturer exceeded the maximum pressure that should have been used for testing the valves."
The author said the replacement rubber diaphragms would need to be brought in from as far away as Australia and Israel.
In addition, the memo identified a malfunction in the software that controls the ventilation system and deluge pumps.
Further detail was provided in a subsequent memo:
"During the commissioning testing of the tunnel ventilation system which is primarily made up of large Jet fans mounted to the roof to the tunnels we have experienced an intermittent fault with the [redacted].
"We found on a number of occasions over time that these units were faulting which meant we lost control of the fans and only by physically going to the units and cycling the power to them could we reset them."