Hollywood star Matt Damon is hunting for some "great character faces" for a feature film he is making with director Gus Van Sant said to be critical about fracking for natural gas.

In a notice seen Friday on the website of the Pittsburgh Film Office in Philadelphia, the casting team of "Promised Land" announced an open audition for paid extras on Saturday at a local convention center.

"We are especially searching for great character faces, farmer looks, senior citizens, baseball players, upscale men and women with formal wear, teens and kids," it said.

"Promised Land" stars Damon -- who Van Sant directed in "Good Will Hunting" -- in a story he co-wrote about a businessman who "experiences live-changing events after arriving in a small town," the IMDb.com website said.

Filming gets underway April 23, according to a Facebook page set up by the casting team in Pennsylvania, one of the eastern US states where fracking for gas is under way.

Earlier this week, in the home stretch of their fundraising campaign on Kickstarter, the makers of pro-fracking film "Frack Nation" stated that "Promised Land" would be "an anti-fracking Hollywood blockbuster."

Spokesmen for Damon and his project could not be reached for comment.

Fracking, or hydraulic fracturing, is a controversial process by which high-pressure injections of water, sand and chemicals are used to blast through rock to release oil and gas trapped inside.

Pennsylvania filmmaker Josh Fox raised concerns about fracking's disputed impact on the environment, particularly underground sources of water, in his Oscar-nominated 2010 documentary "Gasland."