A 21-year-old man was killed on an Amazonian Indian reservation in western Brazil, and police said Tuesday that a witness to the attack claimed the victim was partially eaten by the Indians.

Ocelio Alves de Carvalho was killed Feb. 3 on the Kulina Indian reservation, said Jose Carlos Correia da Silva, the military police commander in the small city of Envira in Amazonas state.

Silva said an Indian who witnessed the killing — and tried to stop it — arrived at the police station to report the alleged murder the next day. The witness said body parts were roasted and eaten, Silva said.

"He was decapitated and cut in half," Silva said the witness told him. "After this, his internal organs, his heart, and parts of his thigh were cut away and eaten."

Silva said five suspects escaped into the jungle, and their motive was unknown. He said that the witness said the suspects had been drinking heavily.

What remained of Carvalho's body was retrieved by relatives two days after the alleged murder and taken to a hospital, where Silva said he examined them.

According to Brazilian law, civil and military police are not allowed onto an Indian reservation without permission from federal officials. Silva said investigators did not receive that permission until about five days after the incident, which is why family members felt compelled to search for the body.

Cannibalism is unheard of among the Kulina tribe — or any Brazilian Indian tribes — according to Brazil's National Indian Foundation, which said in an e-mailed statement it is "investigating the possible involvement of Kulina Indians in the youth's death."

A man who answered the phone at the military police station and said he was Carvalho's uncle confirmed the account of retrieving the body, but he asked not to be named, saying he feared retribution from the suspects.

Silva said it was not until Feb. 8 that a foundation official arrived, granting permission for him and his agents to enter the reservation and question indigenous leaders. Silva said he asked that they remain on the reservation for the near future to avoid violent clashes with people in town.

Maronilton da Silva Clementino, chief of staff at the Envira mayor's office, confirmed Carvalho's death and said the city has been tense since the killing.

"There is at times violence between the Indians and people in town, but we've never seen a case this cruel," he said. "The case is so strange and cruel, at first nobody could believe it."