The accusations have caused widespread criticism of China's booming child education industry.
Several parents found needle marks on her children's bodies, Caixin media group, which initially reported the story, said on Thursday.
RYB posted on its official account on Friday morning, apologizing to parents and stating that they are cooperating with police and taking the case seriously.
RYB immediately provided the security monitoring content and surveillance devices to police authorities, suspended the staff who allegedly were involved, and will continue to take all other necessary measures to promptly cooperate with police and other authorities on the investigation. Police said they were still looking into this accusation.
Meanwhile, RYB Education released its own statement after incidents of abuse surfaced.
Separate incidents in China of children being slapped, beaten with a stick and having their mouths sealed shut with duct tape have also gone viral and fuelled anger online. "They exposed problems in the management of kindergartens", the Chinese Education Ministry said later on Friday, as cited by Xinhua. "The childcare industry can not be allowed to grow in an uncivilised fashion".
Shares in RYB are up about 44 percent on the New York Stock Exchange since a September listing, giving it a market value of almost $766 million.
This isn't the first time that one of its preschools has been accused of abusing students.
Later on Thursday Chinese media cited a local education official who said that at least three teachers at the nursery had been suspended.
On Friday, one father leaving the school said he had been there to cancel his son's enrolment and demand a refund. Four teachers at a RYB kindergarten in Siping in the northeastern province of Jilin were jailed for 30-34 months in October past year over "mistreatment of students", after needle marks were found on some students in November, 2015.
"As a mother when I saw this news I really couldn't take it", she said.
It provides 1,300 daycare centers - some under franchise - and almost 500 kindergartens in 300 Chinese cities, according to its website.