Canada, after years of prodding by the Jewish community, is stepping up investigations of suspected Nazi war criminals, some of whom are believed to be living openly here.

The federal government disclosed this month that it is checking the backgrounds of 110 people, sought chiefly by West Germany and the Netherlands for alleged crimes during World War II.

Disclosure of the large-scale investigation reflects an increased sensitivity to charges that this country has become a "Paraguay North," an allusion to the South American country where several Nazis have turned up.

A senior official of the government of Prime Minister Pierre Elliott Trudeau acknowledged that war criminals are living in Canada. The most widely accepted estimate, from police and the Canadian Jewish Congress, puts the number at about 100, although Simon Wiesenthal, the well-known Nazi hunter, has placed the figure at 1,000.

What angers many of this country's 270,000 Jews is that until last year, not a single arrest had been made in Canada since the war in connection with such crimes.

"We welcome the investigations," said Alan Rose, an official of the Canadian Jewish Congress in Montreal, "but they're 25 years too late."

He said his group and others have been trying for many years to alert Canadians to the fact that "mass murderers" were living among them and "as a reward for their murderous activities had gotten Canadian citizenship."

A precedent-setting case began last summer when Helmut Rauca, a 74-year-old former Gestapo officer, was arrested at his home in Toronto.

In November, the Supreme Court of Ontario Province ordered Rauca, now a naturalized Canadian, extradited to West Germany, where he is accused of responsibility for the deaths of 11,584 Jews in Lithuania, now part of the Soviet Union.

A decision by the Ontario Court of Appeal is expected soon on a bid by Rauca to overturn the order. If the court rules in the government's favor in this first extradition attempt, it would broaden what the government sees as its current limited options.

Officials say existing law is insufficient to permit arrest and trial here of persons accused of war crimes committed in other jurisdictions.

It has been widely noted that Rauca lived in Canada under his own name without incident despite inquiries about him from West Germany dating back almost 10 years. "It took them years to find Rauca, when his name was in the phone book," Rose said.

The Toronto-based Canadian Holocaust Remembrance Association rejects the Liberal government's interpretation of the legality of prosecuting war criminals here. On the contrary, the group says, the Canadian War Crimes Act and the Geneva Convention Act give the government ample legal basis to bring ex-Nazis to trial in Canada.

A principal objection to Ottawa's preferred tactic is that a substantial number of the war criminals believed to be here are, in effect, immune from arrest. This is because their alleged crimes were committed in countries now part of the Soviet Union, with which Canada has no extradition treaty.

Partly for this reason, the Holocaust Association accuses the Liberals of "posturing" on the issue. It will press for a judicial review to settle the question of the government's powers.

Nonetheless, there is no doubt that the Trudeau government has tried in the past few years to extend its cooperation in the hunt for ex-Nazis, improving communications channels with West German officials and with Wiesenthal, who has refused to set foot in Canada because of its alleged apathy on this issue.

Concern about harboring suspects continues to be fanned by publicity, most recently from a Dutch government inquiry about Jacob Luitjens, who lectures at the University of British Columbia in Vancouver. Luitjens has denied charges that he collaborated with the Nazis.

Canada's conscience has been stirred by a recent book, "None Is Too Many," detailing this country's record in accepting refugees from Europe during the years of Nazi terror between 1933 and 1945. During that period, Canada, a huge, underpopulated nation, took no more than 5,000 Jewish refugees because of apparent government fear of arousing anti-Semitism among voters.

Observers speculate that Ottawa took little action on war criminals in years past because the government may have been embarrassed to face up to the question of whether ex-Nazis seeking to avoid prosecution were allowed into Canada in substantial numbers.

Some political leaders warn of starting a "witch hunt" for people now of advanced age on the basis of crimes alleged to have taken place long ago. Rose said, however, that he is convinced Canadians are increasingly "unhappy about having these people living next door to them."

"After all," he said, "Rauca is suspected of killing more people than Klaus Barbie," a reference to the former Gestapo officer whom Bolivia recently sent to France to face charges of crimes against humanity during the Nazi occupation of that country.