Forty people are being investigated over child sex abuse dating back 20 years in Rotherham.
The National Crime Agency (NCA) said 38 men and two women had been arrested or interviewed by appointment over the past two months.
The inquiry relates to child sex abuse and exploitation offences on 13 victims, between 1997 to 2015 when they were aged 11 to 26.
All have been bailed or released under investigation as inquiries continue.
The NCA said the individuals were aged between 29 and 53 and were from Sheffield, Rotherham, Leeds, Dewsbury and Maidstone.
The inquiry is part of Operation Stovewood, which is the largest law enforcement investigation into non-familial child sexual exploitation in the UK.
It is run by the National Crime Agency and has so far identified more than 1,500 potential victims in Rotherham.
To date, 14 people have been convicted and 13 more are awaiting trial.