CONWAY, Ark.—Police say a man posing as an undercover police officer scammed guests staying at two Conway hotels into giving him their money to check for drug residue, a crime matching similar thefts across Arkansas in recent weeks.

Police Lt. Danny Moody says the man showed a badge and a handheld radio to victims, saying they had money that may have been used in a drug buy. Moody says the man promised the victims—a person from South Carolina and a group from Texas—that he would return the money after a drug dog “sniffs” them for illicit substances.

The man never return...