Colorado became the nation’s first state to permit the sale of recreational marijuana, starting Jan. 1.

And since then, interest in travel to Denver has soared.

Coincidence? Probably not.

A data research company found that searches for airline travel deals to Denver have been outpacing searches for all other U.S. destinations, with a big surge starting Jan. 1.

The study by Hopper Research in Boston found that interest in travel to Denver climbed 6.3 percent above the national average in December and then jumped 14 percent during the first week in January. The study looked at billions of travel queries through online travel sites and bricks-and-mortar travel companies.

The interest in traveling to Colorado has been higher in some cities than others.

The biggest increase came from Nashville (63 percent increase), Minneapolis (58 percent), Detroit (53 percent) and Cincinnati (47 percent), according to the study.

Patrick Surry, Hopper’s chief data scientist, said it may not be a coincidence that some of the cities with the biggest increases in travel searches to Denver have strict drug laws.

“We can’t say the intentions of the people looking for those flights,” he said. “But this suggests that it might be a reaction to the demand” for marijuana.