BOGOTA (Reuters) - Colombia’s attorney general has launched a criminal investigation into the deaths of a whistleblower and his son at the center of a corruption probe involving Brazilian construction firm Odebrecht, it said late on Tuesday.

Jorge Enrique Pizano, a witness in one of Latin America’s biggest corruption cases, died last week at his home near the Colombian capital Bogota. Local media reported at the time that he had died of a heart attack.

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 has been at the center of Latin America’s biggest graft scandal since acknowledging in a 2016 leniency deal that it bribed officials in a dozen countries. Odebrecht did not immediately respond to a request for comment on this story.

The attorney general’s office said in a statement it began an immediate investigation into the death of both Pizano and his son when it was informed that the son, Alejandro Pizano Ponce de Leon, died on Sunday after returning from Barcelona to attend his father’s funeral.

It said that the younger Pizano drank from a bottle of water on his father’s desk and was dead from cyanide poisoning within minutes.

The hospital where the elder Pizano was taken shortly after his death said in a statement on Wednesday they had turned over tissue samples from an autopsy to the judicial police.

HIGHWAY PROJECT

The project Pizano 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.

Pizano had given an interview to local television channel Noticias Uno, which was broadcast on Monday but which the channel said was recorded in August. Noticias Uno said Pizano insisted the interview could not be released until he was outside Colombia or dead, citing fears for his safety.

In it, Pizano said he raised suspicions about payments made to unknown recipients by the Brazilian builder in 2013. He said he had informed Nestor Humberto Martinez, who was then Grupo Aval’s legal adviser.

Martinez became Colombia’s attorney general in 2016, after leaving his post with Aval. He has recused himself from the Odebrecht probe due to his prior role.

Pizano in 2015 had secretly made recordings of Martinez that he shared with Noticias Uno.

In the recording, Martinez wonders whether the payments Pizano discovered were connected to paramilitary groups or government officials. Many companies in Colombia, including some multinationals, have been accused of paying bribes to paramilitaries to avoid security problems in restive regions.

“We don’t know if they are paying money to the paramilitaries, if there’s corruption, if they’re stealing,” Martinez said on the recording.

Martinez said in a statement on Monday that he had helped Pizano pass information to Grupo Aval.

Grupo Aval said late on Tuesday that it supports all investigations into the payments but rejected any suggestion it had knowledge of them before they became public.

Odebrecht is suing Colombia for $1.3 billion, alleging the country illegally expropriated assets. Eight people involved in the Odebrecht corruption scandal have been jailed in Colombia, including an ex-senator and a former transport minister.