Rio de Janeiro police said Jonas Junias Jonas, of Namibia, grabbed and kissed the housekeeper while she was cleaning his room, according to the Brazilian news agency Agencia Brasil.
The is the second arrest of an Olympic boxer on charges involving sexual assault within four days.
Police took Jonas to the Bangu penitentiary complex west of the city, Agencia Brasil said. Jonas, a light welterweight who competes in the 64 kilogram class, has a boxing bout scheduled for Thursday.
Mario Andrada, spokesman for the Local Organizing Committee, said the committee is aware of the arrest.
"He has been detained by the local police under the charge of sexual assault," Andrada said. "Brazilian law needs to be respected."
Saada, 22, was arrested and detained under a temporary warrant at the request of the Rio de Janeiro police. The warrant is valid for 15 days.
Saada's attorney, Paulo Freitas Ribeiro, said his client denied wrongdoing during an official statement to the local police.
Saada, a light heavyweight, was scheduled to fight Saturday against Turkish boxer Nadir Mehmet Unal.
Ribeiro tried to obtain a release order to enable Saada to make the fight, but Saturday's boxing results
showed the 23-year-old Unal was declared victor in a "walkover," meaning he won by default after Saada did not appear for the contest.
In the arrest warrant, Judge Larissa Nunes Saly said the detention was necessary because the athlete doesn't have a fixed residence in Brazil.
Nourddine ben Abdelnbi, head of the Moroccan Mission at the games, said the alleged incident happened when maids were cleaning the room where five boxers were staying.
Saada contended their only interaction occurred when one of the maids asked him for a Moroccan flag, Abdelnbi said.
Abdelnbi said that while Saada is in Brazilian custody he is not formally arrested on charges. He is in what Abdelnbi described as "interrogation sessions."
The Moroccan delegation believes Saada is innocent and is awaiting the results of the investigation, Abdelnbi said.
Agencia Brasil, Brazil's official news agency, reported the Rio 2016 Organizing Committee was aware of the case and will cooperate with the police investigation.