LONDON : Sci-fi series "Silo" will return for two more seasons, with the third chapter already shooting in the UK.

Apple CEO Tim Cook joined the series' star and executive producer Rebecca Ferguson on the sprawling "Silo" set at Hoddesdon Studios outside London to make the announcement.

"We feel great about it. We could not be more pleased. We're already filming season three," Cook told Reuters in an interview in the show's Silo 18 cafeteria.

"We get to walk around these environments again under new circumstances, new threats," added Ferguson. "We're back on the show and it's tense, it's wonderful and it's mysterious."

The dystopian drama is based on American author Hugh Howey's "Silo" book trilogy and is set deep underground, where the last remaining people have been sheltering for hundreds of years from what they are told is a toxic environment on the surface of the Earth.

Ferguson plays engineer Juliette, whose suspicions are aroused when she seeks answers to a loved one's death, and she becomes determined to expose the secrets of the silo. Season one ended with Juliette stepping outside of Silo 18 and the second season, currently streaming on Apple TV+, sees her world upended.

The fourth season will conclude the series, the makers said.

Five years on from the launch of Apple TV+ in November 2019, Cook said he considered the service to be "successful by any measure".

"Like the rest of Apple, we're about being the best, not producing the most," said Cook.

"We're focusing on the best quality, with the best storytellers, all original. We think 'Silo' is a fantastic example of that and of course the UK is a great place for storytellers and it's a place where people want to work, and so we're doing a lot in the UK," he said.

New episodes of the 10-part "Silo" season two are released weekly, with the show's finale premiering Jan. 17.