Overnight reports from the US allege things became frosty between JB, 20, and Orlando, 37, when they bumped into each other at an Ibiza club.
A video posted by TMZ appears to show the stars exchanging words while surrounded by friends before it cuts out. According to sources, a punch was also thrown although that was not caught on camera.
Neither Justin nor Orlando have commented, although Justin is alleged to have uploaded a picture of Orlando's ex-wife Miranda Kerr to his Instagram shortly after their encounter - and then swiftly deleted it.
According to various rumours, the altercation was to do with Miranda, with sources claiming Orlando wasn't happy about Justin's interactions with Miranda in the past.
Orlando has also been seen recently in LA hanging out with Justin's ex-girlfriend Selena Gomez.
Oh, guys, what is going on?!
Justin is keeping everyone in the dark by carrying on via Twitter and Instagram as normal - bar the alleged blink and you'll miss it Miranda post.
Overnight, he posted four images to Instagram with no reference to Orlando, Miranda or any altercation. One was a gorgeous scenery shot of Ibiza, while another was a tribute to best friend Khalil.
Alongside the image, he wrote: "This is my brother for life @khalil .. real, true and has one of the biggest hearts I know.
Finally, a photo shows him boarding a private plane, perhaps suggesting he's jetting out of Ibiza.
So, did this alleged fight happen or not? Will Justin or Orlando ever address it? We guess we'll have to wait and see...
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