"We weren't sure when he was coming back, but we realise now it was for an extended period so we've made arrangements for one of the executive staff to be acting chief executive."
Harris said he could not comment on Flowers' personal health issues.
In May, Harris confirmed Wintec would relaunch an investigation into historic allegations about its chief executive Mark Flowers after a peer review found the initial process carried out in 2015 was lacking.
Harris said at the time new investigation would be carried out with urgency and planned to confirm the process within a few weeks.
"Process is important. It's certainly my expectation that I would like to have this resolved as quickly as possible, but once we enter the process - and you have to allow that to run its course - again in fairness to the various parties," Harris told the Herald at the time.
Wintec has declined to release details of the complaints and allegations relating to Flowers, citing confidentiality and privacy.
Meanwhile the outcome of an audit investigation also looking at Flowers' travel expenses to Asia between 2009 and 2017 is overdue and the outcome is still unknown. The $80,000 report has been delayed once already and was expected to be completed by Audit NZ by July at the latest.
The Audit NZ report includes looking at expenses incurred by the chief executive and his executive team between 2009 and 2017 in relation to travel to Hong Kong and China.
Any other travel taken by the chief executive and his executive team between 2013 and 2017 is also being explored.
Audit NZ has also been told to look at whether the redundancy and severance payments, including those bound by confidentiality agreements, made to staff between 2013 and 2017 meet Wintec's policies and the Office of the Auditor General's standards and good practice guidelines.
Early estimates put the cost of the audit work at $80,000.
Wintec communications director Erin Andersen said the audit assurance work was still in progress and there was nothing to add. However an update relating to a new inquiry into the 2015 allegations was expected shortly.
Review of Wintec investigation into CEO looks at whether council needs to reopen investigation
Wintec to launch independent peer review into complaint relating to CEO Mark Flowers