Three senior managers at Waikato District Health Board raised concerns about the chief executive's spending before he resigned.
Dr Nigel Murray resigned from his $560,000 position on October 5 after an investigation found he overspent on relocation costs from Canada to Hamilton and made other "unauthorised" work expense claims.
The investigation was launched in July by the board after chief of staff Neville Hablous, corporate services executive director Maureen Chrystall and strategic projects executive director Ian Wolstencroft went to board chairman Bob Simcock with the concerns.
According to a letter to all staff posted on the DHB intranet, dated October 13, Simcock praised the trio for taking action "when they saw that some of Dr Murray's behaviours were not in line with the behaviour that we would expect of any member of our staff at the DHB".
It's the first time the three top managers have been named publicly as the staff who complained about Murray's expenses.
"The actions that Neville, Maureen and Ian took are a very good example for our staff of what to do when something inappropriate occurs," Simcock wrote.
The three managers, who were part of Murray's 17-strong executive team, came forward after Murray's executive assistant told Hablous of her concerns over the expenses.
It was her job to file the expenses, which have to be disclosed publicly each year.
"While as an organisation we need to have trust in each other, when that trust is broken it is very important that people are able to raise concerns," Simcock said.
"I understand that the recent attention on the DHB has been frustrating for all of us. I want to thank you all for the way you have continued to do what you do best - caring for our community."
Simcock initially said the trio used protected disclosure legislation to blow the whistle without fear of identification but that was later corrected after Hablous said they simply escalated the executive assistant's concerns.
"We did not go down that route," Hablous told the Herald. "We raised it directly [with Simcock]. We were confident that our confidentiality would be preserved."
Wolstencroft previously worked with Murray during the massive rebuild of Auckland Hospital in the early 2000s.
Hablous resigned shortly before the investigation was revealed by the Herald on July 22 and although he is acting chief executive, is due to leave in January.
He said on Friday he would consider staying on if the interim chief executive thought there was a place for him.
Chrystall said she would have left her top job if Murray returned to his role.
"I made a personal decision that Dr Murray's and my values did not align and if he returned I would resign."
Meanwhile mental health and addictions executive director Derek Wright has been named interim chief executive while the DHB begins recruitment to find a replacement for Murray.
Wright has been at the DHB since February 2016 and has previously worked as general manager of North Shore Hospital as well as in mental health positions internationally.
Simcock said in a statement today the board was unanimous in its endorsement for Wright in the interim role.
Wright said he was pleased to take up the challenge.