Aleksander Jevsek, the head of the criminal police, told the press the investigation initially centred on alleged damages of EUR 3.8m to an unnamed company due to extortion.
Unable to get hard evidence, police resorted to wiretaps, which is how they learnt of extortion and a handover of money, and caught whiff of other possibly unlawful activity involving two more persons.
Moving into action, police arrested today a man just as he was receiving EUR 320,000 in cash from a person he had threatened to kill, and another man who was there at the time of the handover of the cash.
Media reports suggest that the man arrested for extortion was SNS lawmaker Srecko Prijatelj.
Immediately after the arrest, police conducted several house searches, including at the SNS offices in parliament, the party's headquarters and the home of SNS president Zmago Jelincic in the same building.
POP TV reported that this was the first police inquiry on parliament or government premises ever.
Jelincic told reporters as he was leaving parliament building in the company of police that the investigation was "a sting by [Interior Minister Katarina] Kresal".
According to the broadcaster, Jelincic was accidentally caught on wiretaps discussing possibly unlawful activity with his MP, as was Agriculture Minister Pogacnik.
The Agriculture Ministry confirmed criminal police had conducted a house search at the ministry's premises and talked to Minister Pogacnik.
The reason why Pogacnik was questioned, POP TV said, is because he was caught doing political horse trading with Jelincic, through Prijatelj.
Jelincic was said to have demanded of the minister that he arrange land for an aviation museum he wants to build, in exchange for the SNS's support in the upcoming parliamentary no-confidence vote against Pogacnik.
The whole background of the arrests is not known yet, but media reports suggest it has to do with land deals involving the wife of MP Srecko Prijatelj that was later purchased by port operator Luka Koper.
POP TV said Aleksandra Prijatelj was the director of the company Premik net, which bought land on the cheap and sold it on to Luka Koper for a handsome profit.
Luka Koper, at the time headed by Robert Casar, had paid commissions for the land deal worth EUR 832,000. The broadcaster also said Casar was one of the people arrested today.
The arrests are certain to have political implications, especially for Prijatelj, but also minister Pogacnik, who is already under fire for his role in a dog mauling scandal.
Prime Minister Borut Pahor would not comment on the political aspect of the sting today, but said the investigation was being handled by people in charge of such things.
"I do not want to and cannot be informed about [such actions] in advance, as it might present a temptation that I don't want to fall for," he told the press during a visit to a company in Nova Gorica.