Avengers 4 directors Joe and Anthony Russo tweeted out a cryptic picture from the set earlier this week, teasing that the currently unknown title for the film was hidden in the snapshot. While there have been plenty of theories as to the title, there’s no definite answer yet. However, the picture isn't just befuddling fans. Marvel Studios Co-President Louis D'Esposito is also baffled by the image.

D’Esposito tweeted that “I’m looking hard but cannot figure out what’s in the photo. And [the Russo Brothers] won’t tell me." D’Esposito has otherwise been just as tight lipped as everyone else involved with the Marvel Cinematic Universe about the highly anticipated Avengers 4.

RELATED: Avengers 4 Teaser Photo May Have Confirmed War Machine’s Proton Cannon

In addition to containing the title for Avengers 4, some fans speculate that the image contains War Machine's proton cannon, first seen in the iconic 2000 video game Marvel vs. Capcom 2: New Age of Heroes.

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Reshoots on the currently untitled fourth Avengers film started at the beginning of the month and are expected to conclude in the fall.

Directed by Joe and Anthony Russo, Avengers 4 stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Brie Larson, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Paul Bettany, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Karen Gillan, Evangeline Lilly, and Josh Brolin. The film arrives May 3, 2019.