Sara Montiel was originally cast for the role of Teresa and filmed some sequences in the Matto Grosso jungle. There are stills where she is seen handling a big snake, possibly an anaconda, along with Glenn Ford, Cesar Romero and others in the cast. In her 2000 autobiography Sara relates how the production ran out of money in Brazil and everybody was sent back to Hollywood with canceled contracts. Months later she was called to resume filming but by then she had signed with Warner Bros. and could not finish "El Americano." She was replaced by Abbe Lane and her scenes were re-shot.
Arthur Kennedy had begun filming when the money ran out and shooting had to be discontinued. When the funding was finally found, Kennedy was working on another project, so he had to be replaced with Frank Lovejoy.