OTTAWA -- The federal government faced growing calls for answers from experts and political opponents alike on Sunday amid lingering questions about the abrupt reassignment of the military general who was overseeing Canada's COVID-19 vaccination campaign, as well as who may be stepping into his critical role.

The Defence Department announced in a terse three-line statement on Friday evening that Maj.-Gen. Dany Fortin was stepping aside from his role overseeing the delivery and distribution of COVID-19 vaccine doses across the country.

The reasons for his departure were not revealed, aside from a brief mention of a "military investigation."

Prime Minister Justin Trudeau's office and the Defence Department, including Defence Minister Harjit Sajjan's office, have since refused to provide further information, including on the nature of the investigation.

The government has also declined to say when officials became aware of the probe and whether Fortin was vetted before being appointed to lead the vaccination campaign in November. Nor has it yet indicated who will be taking over from Fortin as government across the country to ramp up their immunization efforts.

Experts say the lack of information underscores existing frustration over a lack of transparency within the military and Defence Department, as well as raising concerns about Canada's vaccination effort.

"There is a lot of speculation about what's going on," said Charlotte Duval-Lantoine, an expert on sexual misconduct in the military at the Canadian Global Affairs Institute.

"Dany Fortin had an impact on everyday Canadians because he was responsible for the vaccine rollout. So I think the Department of National Defense, at least in my opinion, has an additional duty to kind of tell us what's going on."

Nobody is expecting the Defence Department and government to reveal the specifics of any allegation, Duval-Lantoine added. But she argued a lack of transparency now undercuts already-shaky confidence that the military will hold top officers to account.

"There's no question that type of secrecy is going to be an additional blow to the legitimacy of the military justice system and how the military regulates itself," she said.

University of Ottawa law professor Penny Collenette, who previously served in prime minister Jean Chretien's office while her husband David Collenette was Canada's defence minister, echoed some of those concerns.

"This is a huge operation we're doing, probably one of the most important ever," she said of the vaccination campaign.

"And we don't know what the allegation is. ... We're all at a loss. So that's a vacuum of information, which is inexplicable to me."

The Defence Department has taken a mixed approach to the release of information about investigations into several other senior officers, revealing details for some cases but remaining tight-lipped about others.

It has also approved media interviews by two female officers who are at the centre of allegations into the conduct of former defence chief general Jonathan Vance and his successor, Adm. Art McDonald despite ongoing police investigations.

Conservative defence critic James Bezan called on the government on Sunday to start answering questions.

"As the sexual misconduct crisis continues to rock the Canadian Armed Forces and now our vaccine rollout, the Liberals' lack of leadership is making the situation worse," he said in a statement.

"Justin Trudeau must be transparent with Canadians. Canadians need to have confidence in our military, and that starts with the government providing information."

Collenette also questioned the government's continued silence over who will replace Fortin, with the Prime Minister's Office, Health Canada and the Public Health Agency of Canada refusing to say who will now oversee the vaccine effort.

The government has insisted the vaccination campaign will not be negatively affected by Fortin's departure, but Collenette worried about the impact on Ottawa's work with the provinces to get vaccines into the arms of Canadians.

"It seemed very odd that there wasn't something that said: `No problem, we have an interim person,' or `No problem, his second-in-command will take over,"' she said. "Just something that lets voters, that lets citizens have some security and some certainty."

Fortin joins a growing list of generals and admirals who have been suspended or forced to step aside in recent weeks, many of them because of inappropriate conduct.

Those include Vance and McDonald as well as Vice-Admiral Haydn Edmundson, who until last week commanded the military's human resources section.

Maj.-Gen. Peter Dawe was also forced to step aside as commander of Canada's special forces after writing a letter in support of a soldier found guilty of sexually assaulting a comrade's wife.

And Lt.-Gen. Christopher Coates retired after concerns were raised about an affair that he had with an American civilian while serving as deputy commander of NORAD.

This report by The Canadian Press was first published May 16, 2021.