Germany today summoned Poland’s ambassador in Berlin for an explanation, and Interior Minister Nancy Fesser spoke with her Polish counterpart about the case of the “trafficking” of entry visas for immigrants that has recently shaken the political scene in Warsaw.

The Polish government has been accused by the opposition of “collusion” in a system through which middlemen were paid to grant visas to migrants on a fast track and without proper vetting. The reaction of the German ministry is, so far, the first international one in a case that has dominated the domestic political scene.

Germany is urgently seeking clarification on how many visas were issued and the nationalities of their recipients, sources familiar with the matter said. He also wants to know what measures the Polish government is taking. Chancellor Olaf Soltz’s government is seeking “a swift and complete” briefing on “serious allegations of possible fraud,” one of the sources said, speaking on condition of anonymity.

When asked to comment on Berlin’s stance, Poland’s Deputy Foreign Minister Arkadiusz Mularczyk told state news agency PAP: “It’s about clarifying the accusations that some Polish and German media are hurling, completely unfairly, against Poland in the context of the migration crisis. The ambassador explained that these are unjustified accusations. “I think it reassured our German partners and that was the purpose of the meeting,” he added.

Germany has already expressed concerns about the issue and deployed hundreds of border guards to the border with Poland.

The scandal erupted as the ruling nationalist Law and Justice (PiS) party seeks to secure a third term in government in parliamentary elections on October 15, taking a hard line on immigration. Last Friday, the Foreign Ministry announced that the head of its legal service had been fired and all contracts that had outsourced visa issuance were cancelled. The day before, seven suspects were prosecuted for irregularities in the issuance of visas to immigrants, while two weeks earlier, an investigation was conducted at the Ministry of Foreign Affairs and a deputy minister was dismissed.

PiS accuses opposition parties of “magnifying” the issue and claims some of the problems date back to when the current opposition was in government. But in a clear sign that he is admitting some involvement, Interior Minister Maciej Vasic said that sacked deputy minister Piotr Vavrczyk bore “at least the political responsibility for the visa issue”.