“Two guys came in with duffel bags,” Jason Valentin, an employee at a Duane Reade five blocks away, said of a recent encounter. “I saw them and they saw me. They dumped the ice cream on the floor and ran out.” There was only one thing he could do. “Pick it up,” Mr. Valentin said. “Put it back.”

Deputy Chief Joseph V. Dowling, with the Police Department’s grand larceny division, said detectives were investigating businesses that may be acting as fences for the ice cream, paying about 25 cents on the dollar.

“They go and resell it to local mom-and-pop stores, bodegas, delis, things like that,” he said. “They transport it in freezer bags with dry ice or those frozen packs. You’re traveling to sell it.”

Thefts got so bad in recent weeks at the New York City grocery chain Gristedes that its owner, John A. Catsimatidis, announced a $5,000 reward for information leading to the apprehension of thieves who had targeted his stores. And on Aug. 21, the police arrested a man and a woman on charges of stealing ice cream from a Gristedes.

Mr. Catsimatidis paid the reward to a worker at a bodega who had flagged down the police after, the employee said, the suspects tried to sell stolen ice cream — hot ice cream, as it were — to him.