Michigan has sent letters to 2800 residents ordering them to pay the two-dollar-a-pack cigarette tax on their Internet tobacco purchases.
The letters seek an average of $3200 from each buyer.
A department official says the crackdown that started in February has netted $2.5 million.
The state eventually could target thousands more Michigan smokers as more vendors respond to subpoenas demanding information about online cigarette purchases.
Two Web sites have supplied the names of about 12,000 Michigan residents who bought 582,000 cartons.