OTTAWA -- Beyond expressions of sympathy, the Harper government and the Canadian Forces appeared at a loss Thursday to explain a number of suicides this week among veterans of the war in Afghanistan.

The latest case involved a senior non-commissioned officer at Canadian Forces Base Petawawa, northwest of Ottawa.

The army identified him as Warrant Officer Michael McNeil of 3rd Battalion, Royal Canadian Regiment. Since the death occurred on the base, military police are investigating.

A Defence Department investigation into two other deaths in Western Canada is currently underway, a sombre and visibly moved Defence Minister Rob Nicholson told the House of Commons.

"Our thoughts and prayers are with the families, friends and colleagues of these departed individuals, and I wish all those associated with those individuals peace during this difficult time," Nicholson said.

Earlier in the day, Nicholson called the deaths "very troubling," but noted that since 2011, the Conservative government has poured millions of extra dollars into the treatment and counselling of returning soldiers.

The commander of the Canadian Army was equally upset.

"I am disturbed by the loss of three of our soldiers," said Lt.-Gen. Marquis Hainse.

"The Canadian Army cares deeply for each and every member. It goes without saying that we take every death seriously and as such we will explore all facets of these situations to try and learn from them and reduce future occurrences, while also providing the best support to the Army family whenever a death does occur."

Figures released by National Defence last summer reported that 22 full-time members took their own lives in 2011. The numbers for 2012 have not been made public.

Some have questioned the data because the figures apply only to regular force members, excluding reservists whose part-time designation means they fall under the jurisdiction of civilian agencies in their home provinces.

The RCMP are investigating the death Tuesday of soldier at a home just outside CFB Shilo in Manitoba. Authorities did not release the soldier's name, but friends have identified him as Master Cpl. William Elliott.

Authorities in Alberta, meanwhile, are looking into the case of an artillery soldier who died in hospital Monday after he was found in distress at a correctional centre in Lethbridge. The man, identified by friends as Travis Halmrast, was being held on charges of domestic assault when he died.

The military will undertake boards of inquiry into each death -- routine procedures that look at the circumstances and systemic issues that may have led to a particular incident.

That's not good enough for NDP defence critic Jack Harris, who accused the government of failing its wounded soldiers. Some 50 military inquiries into suicides since 2008 remain incomplete, Harris said.

"We have had soldiers who've stood up for Canada when we asked them to do that. We should be standing up for them and I don't think we're doing that," he said.

National Defence was asked on Thursday how many investigations were still outstanding, but no one was immediately available to comment.

Military boards of inquiry are often held behind closed doors and the families of suicide victims do not have automatic access to the findings and recommendations, said an expert in military law.

In Britain, every soldier's death -- whether at home or overseas -- is the subject of a coroner's inquest, which is held in public, said Michel Drapeau, a retired colonel.

It's a better system that allows families, struggling with their loss, to hear all of the unvarnished evidence and to have input, he said.

"The issue here is not to blame the military," said Drapeau, who represents the family of Cpl. Stuart Langridge, a soldier whose 2008 suicide has been the subject of a military police complaints commission hearing.

"The issue is to make sure we learn from each one of these tragedies and prevent the next one."

A number of mental health and defence experts have warned Canada could face a surge in post-traumatic stress disorder among soldiers over the next five years as the after-effects of a decade of fighting in Afghanistan begin to settle in.

Guy Parent, Canada's veterans ombudsman, said both National Defence and Veterans Affairs need to anticipate the flood, but he was coy when asked whether he believes the steps taken to date have been sufficient.

"They're getting ready," Parent said.