Kato and Sutjiadi were a set down to Marie Bouzkova and Sara Sorribes Tormo but 3-1 up in the second when Kato sent the ball to the opposite end of the court between points, hitting the ball girl and leaving her in distress.
Umpire Alexandre Juge gave Kato a warning before Bouzkova and Sorribes Tormo, on the other side of the net, asked for their opponents to be disqualified.
"No, no, let me explain to you. [Kato] didn't do it on purpose. [The ball girl] didn't get injured," Juge said.
"She didn't do it on purpose? She's crying," Sorribes Tormo said.
"And she has blood," Bouzkova added, prompting the umpire to go to see the ball girl, who was sobbing.
Juge spoke to the girl, and tournament referee Remy Azemar and Grand Slam supervisor Wayne McEwen went to Court 14 to look into what happened. Juge then went back up to his chair and announced the end of the match with the disqualification of Sutjiadi and Kato, who had apologized and was in tears as she left the court.
"It's just a bad situation for everyone," Bouzkova said. "But it's kind of something that, I guess, is taken by the rules, as it is, even though it's very unfortunate for them. ... At the end of the day, it was the referee's decision."
Bouzkova said she did not see the ball girl get hit but added that "she was crying for like 15 minutes."
Reuters and The Associated Press contributed to this report.