According to Don Siegel in his autobiography, Sydney Greenstreet got sick during the shooting of the film and the crew was on lay-off for two weeks without getting paid.
Sydney Greenstreet and Peter Lorre starred in nine films together, the first being The Maltese Falcon (1941) and the last being this one.
There was a major strike in the Warner Bros. studio during the production of the film. Don Siegel and the crew had a problem getting through the studio's fence.