MINNEAPOLIS (AP) -- Several large marijuana busts along Interstate 94 have authorities in North Dakota, Minnesota and Wisconsin wondering whether the interstate corridor is becoming a major smuggling pipeline for marijuana and other drugs.

Authorities think more residents in the three states are buying marijuana where it's legal and then bringing it back home to distribute.

Minnesota troopers seized more than 2,600 pounds of marijuana last year, more than six times what was confiscated the year before. North Dakota troopers confiscated 300 pounds last year, an 88 percent increase from 2016. Wisconsin troopers saw a 20 percent increase in drug arrests from 2016 to 2017.

While Minnesota legalized medical marijuana in 2014, recreational use remains illegal in Minnesota, Wisconsin and North Dakota.