Melissa Leo has joined Will Smith in the cast of "Supermax," an action-thriller from Amazon MGM Studios and Miramax directed by David Gordon Green. The film centres on two FBI agents investigating an apparently impossible murder inside a maximum-security prison, and marks another high-profile addition to a project that has been steadily assembling a strong ensemble cast since Amazon MGM paid $70 million for the worldwide rights in May.

Leo's role is being kept under wraps, but she joins previously announced stars including AnnaSophia Robb, Jason Clarke, Jaafar Jackson, Nicholas Alexander Chavez and others. The film, written by David Weil and David J. Rosen and produced by Westbrook Studios alongside The Picture Company, is currently shooting in New South Wales, Australia, and will stream on Prime Video. Leo, an Oscar winner for "The Fighter" and Emmy winner for "Louie," has also recently completed work on "Passenger," "The Mannequin" and "The Rooster Prince."