More than 150 police officers have raided properties in Teesside and South Yorkshire in a crackdown on people trafficking and sexual offences.
Seven people were arrested in Stockton-on-Tees and another in Sheffield in simultaneous raids.
They followed several young women reporting they had been trafficked and raped at different addresses.
Cleveland Police officers were supported by a team from Immigration Enforcement.
All those being held were arrested on suspicion of offences including conspiracy to rape, conspiracy to traffic and blackmail.
Assistant Chief Constable Jason Harwin said: "Clearly, to deploy 150 officers shows how seriously we take this.
"Human trafficking, the exploitation of the most vulnerable in our communities by the most ruthless, will not be accepted.
"To those who traffic in human beings, in human lives, who seek to gain from fear or weakness, our message is unequivocal; we are strong, we are determined and we will bring you to justice."
ACC Harwin said the force had received intelligence that an unknown number of young women had been trafficked within the Cleveland force area for the purposes of sex over a number of months.
Reports said victims were raped by multiple men after being driven to residential addresses.
He said he was unable to give exact victim numbers at this time, or to say if any of them were juveniles.