OTTAWA - With almost 11,000 applications for citizenship and permanent residence in question, federal immigration officials are expanding their crackdown on fraudsters.

"We have identified up to 3,100 Canadian citizens who may have obtained their citizenship fraudulently, and we will pursue revocation for those who have," Immigration Minister Jason Kenney said Monday.

The feds have also flagged about 7,500 possibly bogus permanent residents, many of whom live outside Canada.

"To date, thanks to these investigations, we have removed or denied admission to Canada to more than 600 former permanent residents, and we have denied about 500 citizenship applications where the applicants failed to meet the residence requirements," said Kenney.

To maintain permanent resident status, someone has to be present in Canada for two out of five years. A permanent resident must live here three out of the last four years before applying for citizenship. Crooked consultants often help foreigners establish a fake paper trail to convince authorities that a citizenship or permanent residence applicant is in Canada, when they're often abroad working in a tax haven.

"In Montreal, one of these crooked consultants had actually created a fake address at a building where there was a door and a post box, but if you opened the door, there was a brick wall behind it," said Kenney. "It was a fake - literally a fake address."

Fraudsters hail from about 100 countries, though Kenney says a "disproportionate number" of cases come from Persian Gulf states.

He's even seen flyers from crooked consultants advertising easy-to-get Canadian citizenship as a way to access to public health care and subsidized university and college education.

"I've never heard of these flyers, this kind of pitch being made for other countries," said Kenney. "My impression is that this is a greater problem in Canada."

Meanwhile, Canadians have given the feds about 4,100 tips about immigration fraud through a special tip line that's been operating for about a year.

Kenney says within one day of launching the tip line, authorities got enough information to catch an alleged fraudster after he showed up to take his citizenship oath in Toronto.

Fraud tips can be called in at 1-888-242-2100, or sent through email to Citizenship-fraud-tips@cic.gc.ca