PRAGUE (Reuters) - Slovak authorities released all seven people detained in connection with the murder of an investigative journalist, a police spokeswoman said on Saturday.

Police detained the suspects on Thursday in an investigation into the murder of Jan Kuciak and his girlfriend, who were found shot dead in their home last weekend.

“During the legal timeframe - 48 hours - (police) checked and searched for facts needed for an indictment. After the 48 hours passed, the persons were released from detention,” police spokeswoman Denisa Baloghova said in a statement.

The murder of Kuciak, whose reporting focused primarily on links between businessmen and Slovak politicians, was the first of a journalist in the country.

Thousands marched in Bratislava and other Slovak cities on Friday, demanding swift action in response to a killing that has shocked the country and shaken its government.

Kuciak had been looking into suspected mafia links among Italian businessmen in eastern Slovakia.

His last, unfinished article was published posthumously by Slovak and international media. One of the men named in Kuciak’s report, which probed potential abuse of European Union subsidies and other fraud, had past links to people who subsequently worked for Prime Minister Robert Fico’s office.

The murder prompted demands from Fico’s coalition partners for the resignation of senior officials.