As speculation grows over Antonio Brown's injured feet, the wide receiver's absence from Oakland Raiders training camp appears to be linked to a unique mishap.

Brown reportedly suffered a number of blisters on his feet after entering a cryogenic chamber without proper footwear, team sources told NFL Network's Ian Rapoport. The incident occurred in France before training camp began, ESPN's Paul Gutierrez added.

The information corroborates a report on Tuesday from Chris Simms of Pro Football Talk.

Brown remains day-to-day, Rapoport added, and it is unclear when he'll be given the green light to return to practice.

The veteran wideout has now missed a significant portion of his first training camp with the Raiders. He began on the non-football injury list with what was first reported to be sore feet.

The four-time first-team All-Pro posted a picture on Instagram following a practice last week of his feet covered in blisters, but later deleted the post.

Oakland head coach Jon Gruden said he was "disappointed" in Brown's absence early in camp as his team prepares for the 2019 campaign.