Some were allegedly found with their hands tied and stripped of their clothes, spokeswoman Ravina Shamdasani said
Biles, who won the beam title earlier in the day, claimed an unrivalled 19th world gold following her previous successes in the team, all-around and vault events in Stuttgart.
"This is really the best worlds performance I have ever put out," Biles said proudly after finishing her fifth world championships with five titles.
The 22-year-old Biles plans to celebrate when she gets back home to Texas, where "my mom usually likes to throw a worlds party - whether I want one or not," she joked.
Biles was crowned world floor champion for the fifth time in her career after winning the final by a full point from team-mate Sunisa Lee, who earned silver with Russia's Angelina Melnikova taking bronze.
"I just couldn't move at the end, I was so tired," Biles confessed after her sixth and final event in Stuttgart.
Her double gold success came within a two-hour spell after earlier winning the beam final with China's Liu Tingting, 19, taking silver with 16-year-old team-mate Li Shijia in bronze.
"It meant a lot," said Biles of her gold on the beam. She had to settle for bronze in the event at the 2016 Olympics and last year's world championships in Doha.
"I'm thrilled with that performance, it was probably the highlight" of the week.
Biles worked hard on the beam to rebuild her confidence in the discipline. "To go out there and nail the routine felt really good," she said. Her victories on the beam and floor made Biles the most decorated gymnast in history, surpassing the previous all-time record of 23 world medals won by men's star Vitaly Scherbo of Belarus in the 1990s.
This is the first time Biles has finished a world championships with five golds, but she has said she is "99 per cent" sure Stuttgart will be her last.
Some were allegedly found with their hands tied and stripped of their clothes, spokeswoman Ravina Shamdasani said
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