ATHENS, Ga. (AP) — A Georgia police officer has arrested two people for selling nitrous oxide, or laughing gas.

An Athens-Clarke County officer made the arrests Thursday, the Athens Banner-Herald reports, after spotting people milling around with balloons following a concert in downtown Athens.

The officer observed that the people were holding the balloons closed with their hands, instead of tying them with string.

The officer found a man and a woman in a nearby parking garage selling the balloons after filling them with a gas. The officer said the man initially told the officer that the gas was helium, but he later admitted it was laughing gas.

Nitrous oxide is used medically as an anesthetic and pain reliever. But people also use the drug to get high. Heavy use can cause damage to brain and nerve tissue.

Jail records show the 23-year-old Atlanta man and 25-year-old Miramar, Florida, woman were charged with misdemeanor sale, distribution or possession of dangerous drugs. Each was released Friday after posting bail. It’s unclear if either has a lawyer to speak for them.

Police Lt. Jody Thompson credited the officer’s “very watchful eye” for noticing the activity. On Tuesday, he described the sale of nitrous oxide as a “very rare occurrence” in Athens, although news reports show arrests were made in 2018 for selling balloons of the gas.

The couple had left three children, ages 1, 5 and 8, in a parked car nearby. A state child welfare worker took them into custody.