"We are being cautious as we don't want to cause further damage to our servers," he said.
"These latest issues have likely added several more days to the first step of restoring the network, but these setbacks have shown us that there are lots of unknowns in the process. We still do not have a concrete time for having our systems back up and running."
People who have scheduled elective surgery or outpatient appointments will be contacted if the DHB needs to cancel their appointment. If patients don't hear from the DHB they are asked to turn up as usual.
Mr Lees has reminded people to expect delays when they go to Rotorua or Taupo Hospital, as assessing and treating patients can take longer without electronic access to records.
He said the DHB had received lots of help from neighbouring DHBs, service providers and primary care.