Someone is ripping off Costco customers loading up on cigarettes on Vancouver Island, the head of the Regional Crime Unit says.

Police on Vancouver Island believe the same thief is responsible for a series of unusual cigarette thefts in Victoria and Nanaimo.

More than $10,000 worth of cigarettes have been stolen in four separate incidents over the past four months in Greater Victoria, and investigators believe the same thief is responsible for $40,000 dollars worth of cigarette rip-offs from Costco customers in Nanaimo last year.

Sgt. Gary Schenk says so far police have no suspects, but say the thief has a unique method of operating that appears to link the cases.

The victims are small store owners who bought between $2,000 and $6,000 dollars worth of cigarettes from Costco. Each was robbed within minutes of leaving their vehicle unattended, and in one case, just after he put the cigarettes in a storage area.

"We've got four different examples, or four different cases, where an individual has made a large volume purchase of cigarettes from Costco and apparently been followed from Costco, because they have been a victim of theft of those cigarettes within minutes or very shortly thereafter," he said.

Schenk warns if you're buying cigarettes from Costco on Vancouver Island, it's possible you're being watched.

"In my police service, I can't recall anything quite like this. The closest example I could think of is where people have been targeted after they've been watched making cash withdrawals from ATMs."