(CNN) - Pablo Neruda wooed readers with his romantic poetry, but the latest lines in his story could be ripped from a murder mystery.

The Chilean poet’s 1973 death certificate says prostate cancer killed him.

But his former chauffeur has another theory involving an unknown assassin, a lethal injection and the South American country’s notorious military coup.

On Monday, authorities started putting that theory to the test, exhuming the poet’s remains as part of a high-profile investigation that could take months to complete.

Manuel Araya, the chauffeur, said he’s received threats for making the controversial claim, which has riled some of Neruda’s supporters.

That won’t stop him from speaking his mind, Araya told CNN Chile.

“I am not afraid of anyone,” he said.

Chauffeur: ‘They silenced him’

Neruda died on September 23, 1973, just 12 days after a right-wing military coup ousted socialist President Salvador Allende and brought Gen. Augusto Pinochet to power.

The poet, a Communist Party member, had criticized the coup and Pinochet.

Less than two weeks later, he was dead.

He had been planning to go into exile the next day — and the timing of his death was no coincidence, according to Araya.

Neruda was a well known political and public figure, having served as a lawmaker and diplomat in addition to his literary career, which earned him a Nobel Prize in 1971.

“I believe that Pablo Neruda was murdered, because Pablo Neruda was a very relevant figure in history, as much in this country as in the world,” Araya told CNN Chile. “He was going to go into exile on September 24 and they silenced him before then.”

Thousands of people disappeared or died during Pinochet’s rule, and many have accused his government of using death squads to wipe out political opponents.

Araya alleges that Neruda was poisoned in a clinic where he was undergoing treatment.

That claim and several other alleged discrepancies surrounding the poet’s death drew the attention of Chile’s Communist Party, whichcalled for Neruda to be exhumed.

Evidence suggests that a third party was involved in Neruda’s death, said Communist Party attorney Eduardo Contreras.

Chilean Judge Mario Carroza ordered the exhumation in February.