Japanese judo officials said they had never seen anything like it after eventual champion Rin Maeda appeared to be bitten by her Chinese opponent at the Asian Games.
Maeda was awarded victory in the quarterfinal bout in Nagoya when Tang Jing was disqualified just over a minute into the contest.
Tang appeared to bite Maeda just above the wrist while the pair were clinched on the ground, with Maeda showing the referee visible teeth marks after getting up from the mat.
Judges reviewed the footage and Tang was disqualified.
Japan women's judo coach Maki Tsukada told sports website The Digest that it was a first for her in her long career in the sport.
"At tournaments like the Asian Games there have been incidents in the past where someone gets punched in the face or their eye swells up," she said following Thursday's incident in their -70kg class bout.
"I regret that we hadn't anticipated that something like this might happen."
Tsukada said the bite marks were visible despite Maeda wearing protective tape on that part of her arm.
"It was to the point where we thought she might actually start bleeding, but it didn't go as far as needing disinfection or anything like that," said Tsukada.
"Still, the teeth marks were clearly and firmly there."
Maeda went on to win gold, beating Kazakhstan's Azhar Askhat in the final.
"I entered this tournament with a strong determination to win gold," said the 21-year-old.
"Preparing for a multi-sport event like this was a unique experience, but I was able to prepare properly each day and deliver my best performance."