'World War Z' director Marc Forster won't return for a sequel.

The German-Swiss filmmaker won't be at the helm of the zombie thriller's planned follow-up, according to The Hollywood Reporter, and star-and-producer Brad Pitt says it is still in the early stages.

He explained: ''We are talking about it. We are going to investigate a script. We have a lot of ideas we will cull from. Nobody is writing just yet, but we are compiling our ideas.''

'World War Z' starred Pitt as Gerry Lane, a former United Nations employee who is tasked with discovering the origins of a deadly virus outbreak which threatens to wipe out the population.

The film earned high praise and has grossed $540 million worldwide, however, the big budget movie's production was hampered by delays and extensive reshoots - including the end being entirely rewritten and reshot - and a ballooning budget.

Pitt's co-star Mireille Enos, who plays his wife Karin Lane in the movie, recently confirmed she's been approached to star in a sequel.

She said: ''Right now, I don't know how deep the conversations are going. I've definitely been approached to say, 'This is a real conversation that is happening', and I'd be thrilled [to do it].''