Another mutant has been confirmed to appear in the highly anticipated 'X-Men: Apocalypse.'

Bryan Singer has just posted a new picture on Instagram, showing the director on the set of the movie. His cryptic caption simply said, "Shooting Caliban's place of "business" #Xmen #XMenApocalypse"

In the X-Men comic books, Caliban is an albino mutant who lives in sewers. He was the power to track other mutants and is recruited by Callisto to form the Morlocks. The mutants live in the underground tunnels of Manhattan and are loosely affiliated with the X-Men.

Singer's post immediately started speculations that Callisto and the rest of the Morlocks will also appear in 'X-Men: Apocalypse.'

There has been no casting news on who will play Caliban in the film.

Singer is well-known for posting Instagram photos from the set of his new movie. He recently posted a picture of his two stars Jennifer Lawrence and Nicholas Hoult on Instagram. "Back with the #thekidsinthehall #jenniferlawrence #mystique #nicholashoult #beast #Xmen #XMenApocalypse," the director wrote. Lawrence and Hoult met on the set of 2011's 'X-Men: First Class.'

They broke up in 2014. Despite talks that Lawrence is currently dating Coldplay's Chris Martin, there are speculations that she has reunited with Hoult during the filming of their new movie.

'X-Men: Apocalypse' will also star Michael Fassbender, who just finished filming 'Macbeth.' Sophie Turner, who plays Sansa in 'Game of Thrones,' will play a young Jean Grey. Oscar Isaac, fresh from the success of 'Ex Machina,' will play Apocalypse, an immortal mutant who is expected to be the main villain in the movie.

Other actors confirmed to appear in the film are James McAvoy, Rose Byrne, Kodi Smit-McPhee, Lucas Till, Ben Hardy, Alexandra Shipp, Tye Sheridan, Lana Condor, Evan Peters and Olivia Munn.

The film is scheduled for release on May 27, 2016.