SYDNEY (AFP) - It seemed like a dream come true - a free holiday to Canada complete with new luggage - until the Australian couple involved realised they had unwittingly become drug mules.

Australian Federal Police on Friday said the pair, a 72-year-old man and 64-year-old woman, told customs officials they had some concerns about their bags when they returned to Perth International Airport on Oct 13.

On examination, some 3.5kg of methamphetamine was found stashed within the lining of each bag, which the police reportedly believe were swopped while in Canada.

"The Australian Federal Police will allege the couple were victims of an elaborate scam and were unwitting participants in the drug importation," the police said in a statement.

The authorities said the scam by a bogus Canada-based tour company calling itself "AusCan Tours" apparently targetted older people, offering two tickets to Canada, seven nights' accommodation and new luggage as a prize.

"The organisers of this scam went to great lengths to provide a facade of legitimacy," Perth airport police commander David Bachi said.

"Thankfully the travellers contacted customs and didn't dismiss their concerns, allowing us to make the arrest."

The authorities arrested a 38-year-old Canadian man at the airport the day the couple returned and have since charged him with importing a commercial quantity of a border-controlled drug.

A raid on a hotel in the Perth suburb of Scarborough uncovered documents allegedly associated with the scam, along with electronic equipment, two suitcases (similar to the ones seized at the airport) and A$15,000 (S$17,800) in cash.

The customs director at Perth airport, Ms Jan Hill, warned travellers about carrying someone else's luggage.

"If you've been asked to carry something on behalf of another person, make the right choice and alert local authorities," she said.

"Do not allow another person to pack your bag and do not carry luggage on behalf of another person."