An internal audit is underway to determine whether Canadian Senators are really living where they say they're living.

Saskatchewan Senator David Tkachuk is heading up the audit. Tkachuk asked each senator to prove where they live to determine whether they are entitled to claim living expenses in Ottawa.

The questions started after Mike Duffy and other senators were accused of not living outside of Ottawa but were still collecting extra money for living expenses. Senators can only claim living expenses if they have a primary residence somewhere else.

Tkachuk is looking for proof that senators pay taxes, have a home, health card, and a driver's licence issued in their home province.

"Hopefully a senator meets all or some of these qualifications and has a residency in their home province," Tkachuk said.

Six people currently represent Saskatchewan on the Senate. CBC reached out to all of them and five out of six have said they maintain a primary residence in Saskatchewan.

Tkachuk said he flies home to Saskatoon every week and pays income tax in Saskatchewan.

UPDATE: Senator Wallin talks about residency

Senator Pam Wallin did not answer CBC's written request Wednesday for information about where she lives, however she did speak briefly about the matter on Parliament Hill.

She was a reluctant interview subject, however.

When CBC reporter James Cudmore asked Wallin to talk about the residency issue, she said, "No, I'm not going to get into that," and walked away.

He asked her where she lives and she said "Saskatchewan."

Asked if she had a residence in Saskatchewan, Wallin said: "I sure do."

Asked if it was in Wadena, she said, "You bet it is". Then she continued walking.

Raynelle Andreychuk and Denise Batters said they own homes and pay taxes in Saskatchewan.

Lillian Dyck said she owns and lives in a Saskatoon house.

Pana Merchant said she's lived in the same Regina home for 42 years and has never had a different health card or driver's licence.

Pamela Wallin is the only Saskatchewan senator who did not immediately respond to CBC's written requests, although she spoke briefly to a reporter in Ottawa on Wednesday.

According to Senate expense reports, Wallin claimed more than $15,000 in Ottawa living expenses last year.

If Wallin does live in Saskatchewan, she is allowed to claim up to $20,000 a year for an Ottawa residence. Her travel records indicate Wallin spent more than $20,000 traveling to and from Saskatchewan last year.

Tkachuk is expected to make his audit public by the end of February.