A query is submitted to a search engine, where the query includes an identification of a symbol. A bounding box is generated in an unlabeled image returned by the search engine in response to the query. A confidence score is also generated that indicates a likelihood of the symbol being present in a portion of the unlabeled image enclosed by the bounding box. The unlabeled image is selected as a training image for training a system to recognize the symbol, when the confidence score is above a predefined threshold.