Back in January, we reported that director Matthew Vaughn and the entire cast of X-Men: First Class will return for the sequel, X-Men: Days of Future Past. Today, we have word that Matthew Vaughn has bowed out of making the sequel. There was no reason given for why he dropped out.

20th Century Fox is said to have Bryan Singer on the top of their short list to replace the director. Bryan Singer and Matthew Vaughn are both still attached to produce, alongside Lauren Shuler Donner and screenwriter Simon Kinberg.

RELATED: Black Widow Actor Claims to Be the First X-Men Mutant in the MCU

The Days of Future Past comic book story line takes place in an alternate future where mutants are hunted down by Sentinels. No concrete story details have been released for this sequel as of yet.

We reported in April that production will begin in January, after X-Men: First Class star Jennifer Lawrence wraps on The Hunger Games: Catching Fire.

Matthew Vaughn is still planning on directing another movie for Fox, which may be Secret Service, an adaptation of Mark Millar's comic book series. Both the author and filmmaker have been developing the project, although it is not known when it will go into production.