I saw this a few times as a kid on afternoon TV in the 60's. I'm thinking it must've been a movie from the 50's or possibly even the 40's... and to be honest it may have even been an episode of some TV show during that time period. It was a crime drama where the bad guys had pulled off a robbery or something and then were trying to make their getaway by hiding in a secret compartment inside the tanker trailer of a a gasoline truck. There was actually gasoline surrounding the secret compartment so that if the authorities opened the top of the tanker it would appear normal. But during the getaway a leak develops and fills the compartment and all the bad guys drown.
