The family of Chilean Nobel literature laureate Pablo Neruda says the leftist poet must have died after having been injected with a highly aggressive, penicillin-resistant bacterium in September 1973, just days after the Pinochet dictatorship came to power.

"The investigation represents a major advance because it contradicts the official story that Neruda died of (prostate cancer). With all these new (elements), we think that there indeed was third-party intervention," Rodolfo Reyes, Neruda's nephew and plaintiff in a case aimed at determining his cause of death, said at a press conference Friday.

Next week, a group of experts from Denmark, Spain, Canada and the United States will travel to Chile in an attempt to ascertain where the Staphylococcus aureus bacterium found in Neruda's bones may have originated.

That bacterium was used by Eugenio Berrios, a secret-police chemist and agent in Gen. Augusto Pinochet's 1973-1990 regime, to eliminate opponents of the military dictatorship, the attorney of the Communist Party of Chile, Eduardo Contreras, said.

Neruda, a member of the Communist Party since 1945, had been hospitalized eight days after the Sept. 11, 1973, coup that ousted Socialist President Salvador Allende.

He was being treated at the Santa Maria clinic, a hospital in Santiago that had been taken over by military.

Forensic experts from Spain's University of Murcia detected evidence of a massive bacterial infection in Neruda's remains during tests conducted in May as part of an investigation by Chilean Judge Mario Carroza to determine the precise cause of the 1971 Nobel literature laureate's death on Sept. 23, 1973, at the age of 69.

A group of Chilean and international experts concluded in November 2013 that Neruda - whose remains had been exhumed in April of that year - had not been poisoned, but Carroza ruled that their results were not conclusive and ordered new tests.

Neruda was awarded the Nobel Prize in literature in 1971 "for a poetry that with the action of an elemental force brings alive a continent's destiny and dreams."