 -- Denver International Airport rental cars appear to be increasingly used as a marijuana dumping ground for travelers. People who want to avoid illegally bringing pot into the airport simply leave it in the car or offer it to the car rental agencies, one Avis Rent A Car airport agent said today.

“We see quite a few cases,” the 18-year Avis employee in Denver, declining to give her name, told ABC News. “We basically don’t touch it. Usually, the manager will take it and flush it down the toilet.

“We are a drug-free environment. We don’t take it or give it back; we just flush it.”

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Recreational marijuana use by adults 21 and older has been legal in Colorado since late 2012. Possession of up to 1 ounce is OK, but it’s illegal to take any amount out of the state.

So some customers offer their leftovers to the rental agents.

“I have had customers come up to the counter and give it to us, asking ‘Do you want it?’” the Avis rental agent said, adding that she immediately declines and offers to help the customer dispose of it.

Denver International spokesman Heath Montgomery said the facility’s formal policy is that “marijuana is not allowed on airport property.”

The airport has seen 16 cases this year of individuals trying to get marijuana through security to take with them, which Montgomery cites as infinitesimally small when compared to the 25 million passengers to date who have passed through.

“No one has been cited,” Montgomery said. “We usually just have them toss it in the trash.”