Slovak police detained seven people on March 1 in an investigation into the murder of journalist Jan Kuciak, police chief Tibor Gaspar said.
The bodies of 27-year-old Jan Kuciak and his girlfriend, Martina Kusnirova, were found on February 25 in their house in Velka Maca, east of the capital, Bratislava.
They had both been shot.
The murders prompted demands from Prime Minister Robert Fico's coalition partners for the resignation of senior officials.
He said on television that the seven suspects were detained during raids in seven locations in eastern Slovakia
Gaspar identified the detainees by their first names and initials and some of these appeared to match names of Italian businesspeople who were the focus of Kuciak's final report.
Gaspar said one of the detainees was Antonino V.
According to the Slovak business registry, Italian businessman Antonino Vadala briefly owned a firm with Maria Troskova, an aide to Fico.
Troskova and the secretary of the country's Security Council, also mentioned in Kuciak's reporting, resigned on February 28 pending results of the investigation. Both Troskova and the secretary have denied any wrongdoing.