The 'Dick Tracy' actor - who has had a decade away from appearing in films - has been meeting with stars including Andrew Garfield, Annette Bening - his wife - Alec Baldwin and Shia LaBeouf to take part in the movie, which he will also direct, about the businessman's later years and his dealings with a younger woman.
Little more is known about the film, with Paramount keen to keep details under wraps, Deadline.com reports.
Recently, 74-year-old Warren confirmed he would be working on a follow-up to 'Dick Tracy' - in which he directed and starred - but would not confirm any further details.
He said "I'm gonna make another one. I think it's dumb to talk about movie before you make them. I just don't do it. It gives you a perfect excuse to avoid making them.
"The more you talk about it, the longer it's hidden."