British-American influencer Andrew Tate and his brother Tristan Tate were arrested for 30 days on Friday evening.
This was decided by a court in Bucharest after five hours of interrogation and three hours of deliberation, as reported by the Romanian media, citing the authorities.
Those arrested have 48 hours to appeal the detention.
The evening before, the brothers and two Romanian accomplices were arrested in the Bucharest area.
Prosecutors confirmed to the Reuters news agency that the former kickboxer was suspected of human trafficking, rape and the formation of a criminal organization.
Photos showed Andrew Tate and his brother Tristan being taken away by emergency services in Bucharest.
Pizza box theory just "amusing speculation"
According to a statement by the Romanian public prosecutor's special unit responsible for organized crime, DIICOT, the six victims identified so far were recruited using the so-called loverboy method.
They were lured with promises of love and marriage.
After that, the women and girls were held with violence and intimidation in different apartments around Bucharest.
There they were forced to have sex and appear in pornographic videos, which were then shared on social media.
One of the victims was also raped twice by one of those arrested.
In the past, Andrew Tate has said, among other things, that women are their husbands' property and that rape victims share responsibility.
In paid lessons, he gives tips on how to make money online and how to emulate it.
Videos of him have been viewed online in large numbers for some time now, and time and again his statements are misogynistic and designed to be provocative.
Most recently, he boasted about the number of his cars and wrote to climate activist Greta Thunberg: "Please give me your email address so I can send you a complete list of my car collection and the enormous emissions." The pioneer of the global climate protection movement Fridays for Future responded wittily: "Yes, please enlighten me, write to me at smalldickenergy@getalife.com (smallerpenisenergy@hastdunichtsbettereszutun.com)."
Tate responded with a video of him smoking a cigar and having two pizzas brought to him.
On the boxes is the name of a pizza shop that only exists in Romania.
Several media outlets then speculated that this information helped investigators track down Tate.
However, even in the days before, the influencer on Twitter made no secret of the fact that he was in Romania.
A spokeswoman for the DIICOT public prosecutor's office said to the dpa inquiry about the pizza box theory: "These are amusing speculations." It is not true that the box played a role in the arrest.
Thunberg meanwhile followed up on Twitter and wrote on Friday: "This is what happens when you don't recycle your pizza boxes." Within minutes, the tweet was approved tens of thousands of times with "likes".