Michael Moore is at work on a follow-up to his hugely successful film about the U.S. government response to the terrorist attacks of September 11, 2001, according to Variety.

“Fahrenheit 9/11,” released in 2004, is the highest grossing documentary of all-time. It earned $119 million at the U.S. box office and another $100 million worldwide.

By comparison, “SiCKO,” his most recent documentary about the abysmal state of healthcare in the U.S., earned a paltry $24 million at home and $11 million abroad, according boxofficemojo.com.

Overture Films and Paramount Vantage will co-finance and co-produce the new Moore film, which, according to Variety, “will pickup where ‘Fahrenheit 9/11′ left off.”