Gunsly Milsoit, left, comforts his brother-in-law Leo Pierre on Thursday after Leo's wife and Gunsly's sister, Milsoit Kelly, who was three months pregnant, died when a four-storey building collapsed in Port-au-Prince. (Gerald Herbert/Associated Press)

One of two Mounties who were missing in the wake of the devastating earthquake in Haiti has been found dead, bringing the number of Canadians killed to four.

The body of Sgt. Mark Gallagher was found in the rubble of the residence where he was staying in Port-au-Prince, the capital city, RCMP Commissioner William J.S. Elliott told a news conference in Ottawa on Thursday.

"This is devastating news for Mark's immediate family and those of us in the RCMP," Elliott said. "My profound sympathies go out to Mark's wife, Lisa, and their children Shane and Heather.

"We are now doing everything possible to recover Mark's body and arrange for his repatriation."

RCMP Sgt. Mark Gallagher, 50, died in the earthquake in Haiti, where more than 80 Canadian police officers were teaching law enforcement. (CBC)

Gallagher, 50, spoke to his wife in New Brunswick on Tuesday, just half an hour before the earthquake hit, to say he was going to bed. He had worked as a public relations officer for the RCMP in the Maritimes but went to Haiti because he wanted more of a challenge, his wife told CBC

Prime Minister Stephen Harper reacted with "profound sadness" at news of Gallagher's death. He was one of nearly 100 Canadian police officers in Haiti as part of the UN mission.

"These men and women have left the comfort of their homes and families to dedicate themselves to providing a better future to one of the poorest countries in this hemisphere," Harper said in a statement late Thursday.

"This is the first time that a serving Canadian police officer has been killed on active duty in an international peacekeeping operation."

Another Mountie, Supt. Doug Coates from Ottawa headquarters, was still missing Thursday, said spokeswoman Patricia Flood.

UN spokeswoman Alexandra Duguay and UN worker Jean-Philippe Laberge were also among the Canadians unaccounted for.

Gallagher was the fourth Canadian confirmed dead as a result of the quake. The other three victims include Georges Anglade, a Montreal university professor for 30 years, and his wife, Mireille. They were visiting friends in Port-au-Prince and were killed when the house they were in collapsed.

Yvonne Martin, a nurse from Elmira, Ont., who arrived in Haiti's capital on Tuesday afternoon, about 90 minutes before the earthquake hit, was also among the casualties.

There is confusion around the fate of Serge Marcil, the former Liberal MP believed to have been located after being reported missing in Haiti.

There were reports Marcil had been rescued and flown to Miami to undergo medical treatment. It now appears those reports were premature — perhaps even inaccurate.

Now, it's not clear Marcil has been rescued at all.

Marcil had only been in Port-au-Prince a couple of hours when the earthquake happened. He has been unaccounted for in the aftermath.

Marcil, who is also a former member of the Quebec legislature, was supposed to stay at the Montana Hotel, one of many buildings that collapsed. It is not known if he reached the hotel.

Earlier, Foreign Affairs Minister Lawrence Cannon said about 100 Canadians safely removed from Haiti were expected to arrive in Canada on Thursday evening.

Foreign Affairs Minister Lawrence Cannon, centre, says he expects more Canadian casualties. (Fred Chartrand/Canadian Press)He cautioned there could be more Canadian casualties.

"We are deeply saddened by reports of Canadian casualties as a result of the earthquake in Haiti," Cannon told a news conference. "Unfortunately, the reality in the aftermath of the catastrophic events is that we expect more casualties to be reported as search and rescue operations unfold."

The first wave of Canadians from Haiti arrived in the Dominican Republic on Wednesday night and was transported to Montreal on a Hercules C-130 aircraft. They arrived in Montreal early Friday morning.

The nearly 100 weary evacuees were brought home on the same military aircraft that carried Canadian soldiers into the disaster zone Thursday. A second plane carrying more evacuees followed closely behind.

Some family members waited for hours at Montreal's Trudeau airport for their loved ones to arrive. However, they had to wait to meet their loved ones after the plane landed because the evacuees, many with blankets around their shoulders, were packed aboard a bus at the airport and taken to a nearby hotel.

Priority in the repatriation effort was being given to injured people, women, and children.

The evacuees were selected by staff at the Canadian Embassy, which remains functional despite sustaining damage.

Cannon said more than 100 Canadians in Haiti have taken refuge in the embassy, while another 48 are being assisted.

"Those people who are injured, who need medical assistance, will be the first to leave," Cannon said.

Cannon said 24 staff at the Canadian mission in the Haitian capital were accounted for, as were five military personnel.

Martin was among a contingent of six nurses from the Kitchener-Waterloo area sent to Haiti by the Waterloo Mennonite Brethren Church.

About 6,000 Canadian citizens live in Haiti, but only 700 are registered with the Canadian Embassy in Port-au-Prince, Cannon said.

With files from The Canadian Press