BOGOTA (Reuters) - A Colombian investigation into the death of Jorge Enrique Pizano, a key witness at the center of a corruption probe involving Brazilian construction firm Odebrecht [ODBES.UL], found that he died of a heart attack, the chief coroner said on Friday.

The attorney general’s office on Tuesday had ordered a probe into Pizano’s Nov. 9 death on fears of foul play after his son, Alejandro Pizano Ponce de Leon, died from cyanide poisoning two days later.

The attorney general said the younger Pizano drank from a bottle of water on his father’s desk and was dead within minutes. The son had arrived the previous day from Barcelona to attend his father’s funeral.

The Pizano deaths are the latest twist in a corruption probe that placed Odebrecht at the center of a massive Latin America graft scandal. The company acknowledged in a 2016 leniency deal that it had bribed officials in a dozen countries.

Jorge Pizano, an auditor for the Ruta del Sol II roadway concession in which Odebrecht was a partner, had been assisting prosecutors investigating allegations that the Brazilian firm paid some $30 million in bribes to secure Colombian infrastructure contracts.

Odebrecht offered its condolences over the deaths in a statement on Friday and said it would continue to collaborate with Colombian judicial authorities.

Tissue samples taken during the elder Pizano’s autopsy were tested by two separate laboratories and no cyanide was found, coroner’s office director Carlos Eduardo Valdes told reporters in Bogota. The coroners concluded that the original medical assessment that Pizano had died of a heart attack was correct.

“The two laboratories independently found no cyanide in the analyzed tissues ... in the case of the death of the young man, the blood and bottle were found to contain cyanide,” Valdes said on Friday.

Jorge Pizano had told local television channel Noticias Uno in an August interview broadcast on Monday that he feared for his safety.

The project he audited was a 2010 partnership between Odebrecht and a unit of Colombia’s Grupo Aval, the country’s largest financial firm, to build a 528 kilometer (328 mile) highway to Colombia’s Caribbean coast. The contract was worth about $1.7 billion.