The veteran actor, who played Dr Peter Venkman in the original 1984 movie, was spotted en route to Boston at the weekend, where lead stars Melissa McCarthy, Kristen Wiig, Leslie Jones and Kate McKinnon are shooting new scenes with director Paul Feig.
Details of Murray's role remain vague but it is expected to be minor, with some reports suggesting he will star as a new character called Martin Heis.
Birth Movies Death describes Heis as a "sort of Amazing Randi type who shows up and 'proves' the new Ghostbusters are fakes".
Murray's involvement may come as a surprise to many fans after his disappointment with Ghostbusters 2 in 1989 and recent attempts to dismiss rumours as "crazy talk". He did, however, support the all-female line-up early on, calling it a "swell" idea.
Murray's former co-star Dan Aykroyd filmed his own appearance in Ghostbusters 3 last month, after tweeting that he was on set and the "Lady GBs are adorable, hilarious and badass".
Again, it is unknown whether Aykroyd will return as Dr Raymond Stantz, with Indie Revolver hinting that he is playing a cab driver who yells "I ain't afraid of no ghosts!" out of the window at Wiig.
Wiig and McCarthy are reported to be playing "unheralded authors who write a book positing that ghosts are real" and go by the names Erin Gilbert and Abby Bergman.
McKinnon stars as Bergman's new partner Jillian Holtzmann, while Jones is NYC subway worker Patty Tolan, who unexpectedly meets the movie's biggest supernatural threat.
There is still no word on whether third original ghostbuster Ernie Hudson will also pop up. He originally branded the reboot a "bad idea" but has since expressed his desire to be part of it.
Feig has been sharing photos of the new uniforms, proton packs and car on Twitter and will likely keep teasing fans right up until next summer, when Ghostbusters 3 reaches UK cinemas on 15 July.
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