Oil giant's leaked data reveals 'awful' pollution

The fisherwoman is now protected by armed bodyguards paid for by the government, but the threats have continued.

Asked about the threats Mr Olarte described, the former CEO Mr Bayón said they were "absolutely unacceptable".

"I want to make it totally clear… that never, at any time, was there any order of that sort," Mr Bayón said.

Ms Velásquez and Mr Olarte both know the risks are real. Colombia is the most dangerous country in the world for environmental defenders, according to the NGO Global Witness, with 79 killed in 2023.

Experts say such killings are linked to Colombia's decades-long armed conflict, in which government forces and paramilitaries allied to them have fought left-wing rebel groups.

Despite government attempts to end the conflict, armed groups and drug cartels remain active in parts of the country.

Matthew Smith, an oil analyst and financial journalist based in Colombia, says he does not believe Ecopetrol managers are involved in threats by armed groups.

But he says there is an "immense" overlap between former paramilitary groups and the private security sector.

Private security firms often employ former members of paramilitary groups and compete for lucrative contracts to protect oil facilities, he says.

Mr Olarte has shared internal Ecopetrol emails showing that in 2018, the company paid a total of $65m to more than 2,800 private security companies.

"There is always that risk of some sort of contagion between the private security companies, the types of people they employ, and their desire to continually maintain their contract," Mr Smith says.

He says this could potentially even include kidnapping or murdering community leaders or environmental defenders in order to "ensure that Ecopetrol's operations proceed smoothly".