Samples of Neruda's remains were analysed by researchers from the University of Copenhagen in Denmark and Ancient DNA Center at McMaster University in Canada.
Neruda died in a hospital in Santiago at the age of 69 in September 1973, just days after the military coup that brought dictator Augusto Pinochet to power in Chile, researchers said.
Neruda, also a politician and a diplomat, had been a supporter of the deposed leftist president Salvador Allende, they said.
In 2013, a Chilean judge ordered the remains of the Nobel laureate to be exhumed for an investigation.
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Hours before his death, Neruda reportedly told the driver that he had been injected in the stomach with an unknown substance.
"The immediate cause of death, cachexia, cannot be correct," said Niels Morling, a forensic geneticist at the University of Copenhagen.
"Neruda was an obese man, who should have been recommended a diet - the opposite of cachexia," said Morling.
Neruda, who won the Nobel Prize for Literature in 1971, wrote in a variety of styles, including surrealist poems, historical epics, overtly political manifestos, and passionate love poems.
"Bacteria are present everywhere, and one of the biggest challenges of this case is determining if the bacteria found in the remains stem from an endogenous source or from the surrounding environment, or laboratory contamination," said Debi Poinar, a senior research fellow at McMaster.
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