Lally Weymouth is a senior associate editor for The Post.

Rodrigo Janot, the Brazilian attorney general heading up the biggest corruption investigation the country has ever seen, is known here as “the man who makes Brasília shiver.” This week, in his office in Brasília, he granted his first exclusive interview since 2014 to The Post’s Lally Weymouth . Janot says that he hopes the wide-ranging “car wash” probe into graft and abuse of power will ultimately result in a cleaner and less corrupt country. Excerpts:

Q: Can you talk about how the investigation began?

A: This investigation began in the southern state of Paraná and involved three illegal exchange operators.

They were doing money laundering, right?

Yes. Money laundering and sending illegal money transfers abroad. One of the operators of the illegal exchange worked here in Brasília. Right by his office, there was a gas station with a giant placard saying “car wash” (lava jato). That is where the investigation got its name.

When did it become obvious to you that money had gone from Petrobras [state-owned oil company] contracts to the political parties?

[Our investigators] started clarifying how the scheme worked inside Petrobras for the payment of bribes. The way I see it, Petrobras was a victim of a criminal organization that tried to get a hold of it to make a profit illegally.

Once the medium-sized contracting companies started collaborating, they explained how the system worked, and we found documents that showed they had a system based on the rules of a soccer championship. They called it “the Contractors’ Club.” Each company was a team, and they would play against each other. When a public contract was up, Brazilian law requires that a minimum of three companies bid against each other to see who gets the contract.

So the companies got together and decided who would bid?

It was a fake competition to get the contracts. They would offer prices that were set beforehand, and they knew who would get it. Illegal. Cartel is a crime in Brazil.

Weren’t they giving [kickbacks] to the political parties?

The investigators discovered that the companies figured out there were three types of donations. The first one was actually legal within the legal standards of the time. The other two were illegal. In the case of the second type of donation, some money would be channeled to the political parties through cash or accounts abroad.

Isn’t your political system a presidential system where in order to get bills through Congress, you must persuade other political parties to agree to vote for your bill? And therefore you end up with a corrupt system where you have to give something to get votes. Isn’t there a problem with the system?

Yes, absolutely. It is a systemic problem. If you don’t change the system, we will take down these people, but others will come and replace them.

If there is a change in the system, I will retire very happy, because I will have helped fix and heal this very corrupt system. You have to change the system. Otherwise you will have a few parties down, but there are already other parties who are trying to get into the scheme. There is a saying that is not very polite that “you get rid of the flies, but the [expletive] remains.”

Do all roads lead to [former] president [Luiz Inácio] Lula [da Silva] ? Is he at the top of the pyramid?

We haven’t reached that level yet. We are trying to figure out how the top tier worked, the architecture of the whole criminal organization. We have no doubt it was a criminal organization.

Where are you now?

We are near the top.

You asked to arrest four PMDB members of Congress [and members of interim President Michel Temer’s party] recently, but the Supreme Court said no.

These were temporary preventive arrests. The way we see it, these people were working to obstruct justice in my investigation, but the Supreme Court disagreed.

The president of the Senate said he was going to consider impeaching you, correct?

That is the Senate’s problem.

What happens to Dilma Rousseff, who headed the board of directors of Petrobras between 2003 and 2010?

All investigations concerning Petrobras, bribes and corruption yielded no facts that led to President Dilma. My office is investigating President Dilma at this point for trying to obstruct the investigation of Lava Jato.

When she tried to bring Lula into the cabinet?

Yes. I asked the Supreme Court to stop this, and they agreed. I argued that the investigations related to Lula should remain in the lower courts in Curitiba — not come to the Supreme Court.

In his recent plea bargain, Sérgio Machado, a former senior executive of a Petrobras subsidiary who taped people for over six hours, mentioned interim President Temer.

He mentioned President Temer as someone who asked for a political donation for the campaign of a deputy in São Paulo. As of today, I can’t tell if this was a legal or illegal donation. As of today, there are no facts that can actually affect President Temer.

Do you think you and Judge Sérgio Moro [the magistrate overseeing the civilian aspects of the case] are creating a new Brazil?

A new Brazil must be created by Brazil itself. I am not a politician; I am just doing my job.

I heard that the Brazilian people want to see an end to corruption.

I think there won’t be an end to corruption, but there must be mechanisms in place to limit the scope of it and to prevent it from becoming overwhelming. Here in Brazil, it became endemic.

Does doing this job create risks to you personally? Someone broke into your house and took the control for your gate.

They did break into my house when I was abroad in Florida. All they took was the remote control of the gate. I understood it as a warning because they didn’t take anything else.

There are a lot of powerful people who must hate you.

I take my own precautions. I keep a pistol by my nightstand, with three loaded cartridges with 14 bullets in each.