A four-year-old boy who was been found chained, malnourished and beaten in a Mexico City apartment may be a U.S. citizen.

Mexico City's prosecutor's office said in a statement that it has asked for assistance from the U.S. Embassy in determining the boy's citizenship.

Authorities rescued the boy earlier this week after an anonymous caller contacted the police.

Two people identified as an aunt and uncle were later arrested. They have been named as Juan Carlos Loaeza and Olivia Castro.

A four-year-old boy called Andrew was found tied up and kept hidden in the dark in a Mexico City apartment. He appeared to have been tortured and abused

The boy had a number of blows to the head and cigarette burns on his back. He also appeared to be suffering from malnutrition

Both of the boy's relatives denied that he was in their home at the time, but after some searching police found the boy tied up in an unlit room.

The little boy was found tied up and completely along with signs he had been tortured and abused.

The relatives said they were looking after him temporarily for the boy's dad.

The youngster, named only as Antony, was found in a house on a street named Cabo Catoche in the colony of Gabriel Hernandez, in a neighborhood north of downtown.

He was taken to hospital right away where he was found to have multiple injuries.

Although he found it difficult to speak, the child was able to say his own name and that of his parents.

Doctors found that he was suffering from malnutrition and say the little boy had been hit repeatedly in the head and his skin burned numerous times by cigarettes.

The little boy was found with a chain around his feet and found it difficult to speak. His aunt and uncle have been arrested and the youngster is now in care

The youngster is now in the care of authorities who are helping him come to terms with the level of abuse he has undergone.

A photograph released by care workers showed a silver chain binding his thin legs together.

The investigation was launched when Victor Hugo Lobo, the head of the child protection authority, received an anonymous letter that detailed information about the boy.

Hugo Lobo vowed that the culprits would be punished.

It is not known whether the boy's father has also been arrested, however the investigation is continuing.

The U.S. Embassy in Mexico City did not immediately respond to a request for comment.