While five men, aged 29 to 62, from the Rotherham area were arrested as part of a separate part of the investigation into the alleged abuse of two girls between 2007 and 2009.
Meanwhile, a 51-year-old man has been arrested in Conisbrough, Doncaster on suspicion of sexually assaulting a 14 or 15-year-old girl who allegedly took place in 2008.
The 15 men have been released as investigations continue.
NCA Regional Investigations Manager Rob Burgess said: “This latest operational activity means that we have now interviewed over 190 people as part of Operation Stovewood.
“We have also worked with partner law enforcement and local authorities to take safeguard measures protecting around 40 children over the past two weeks. This is an important part of our work and is often overlooked.
“While our resolve to bring offenders to justice is not diminished, we continue to reach out and call on victims or witnesses to come forward.
“Our investigation is victim-centric and we are interested in speaking to anyone who may have information to assist in the investigation of child sexual abuse in Rotherham between 1997 and 2013. Victims will be supported.”
The NCA launched the independent investigation in 2015 following a request by South Yorkshire Police after a 2014 report by Professor Alexis Jay that abuse in Rotherham was ignored by agencies.