A mother and her boyfriend have been arrested in Argentina over the rape and murder of her four-year-old daughter after they claimed the girl drowned in their swimming pool.

Bianca Xiomara Godoy was rushed to a hospital near Buenos Aires on Friday night but doctors were unable to revive the little girl.

Her mother Viviana Beatriz Roldan, 25, and boyfriend Federico Sebastian Espinoza, 23, told hospital staff that they found Bianca unresponsive in a swimming pool at their home.

Four-year-old Bianca Xiomara Godoy was rushed to a hospital in Buenos Aires, Argentina on Friday night but doctors were unable to revive the little girl

Police started investigating after doctors reported that Bianca had severe injuries that indicated longstanding abuse.

Bianca's body had visible marks, possibly caused by a belt and buckle, and she had abrasions on her throat and bruises on her face.

It also appeared that Bianca had been restrained by her ankles and wrists.

Police also said the little girl also had internal anal injuries that indicated she had been raped.

Investigators questioned both Roldan and Espinoza about the little girl's death.

Following an investigation into her cause of death, police said they believed Bianca suffered a violent blow to her head while she was eating, which may have caused her to choke.

Her mother Viviana Beatriz Roldan, 25, and boyfriend Federico Sebastian Espinoza, 23, have been arrested over the little girl's murder and rape

Police started investigating after doctors reported that Bianca had severe injuries that indicated longstanding abuse. She had visible marks and bruises on her body and had internal anal injuries that indicated she had been raped

Her mother Viviana Beatriz Roldan, 25, and boyfriend Federico Sebastian Espinoza, 23, told hospital staff that they found Bianca unresponsive in a swimming pool at their home

A local policeman told Argentinian news outlet InfoCanuelas that there were no words to describe the abuse.

'What they did has no name. I still have not dared to see the photos of the body... because seeing such a thing is difficult to bear,' he said.

Roldan's sister Micaela Ibanez told Argentinian news outlet Cronica that their family had not seen Bianca since the girl's mother had started dating Espinoza a year ago.

She said Bianca's biological father had been trying to get custody of the girl.

'Viviana completely changed since she started to date Federico almost a year and a half ago. Before then we saw each other all the time but he wouldn't let her see anybody in the family and blocked us all out,' Ibanez said.

Ibanez also claimed that Espinoza also beat her sister and forced her to sell drugs.