BRATISLAVA, Slovakia — Before he and his fiancée were killed in their home, a Slovak journalist was investigating a powerful Italian organized crime group, its activities in his country and its possible ties to Slovak government officials, the journalist’s colleagues said on Wednesday.

The journalist, Jan Kuciak, was looking into whether the ’Ndrangheta, the Calabrian organized crime syndicate, had funneled money into Slovakia, investing in real estate and other ventures, and developing ties to Slovak politicians, according to Aktuality.sk, the news site he worked for, and the Organized Crime and Corruption Reporting Project, one of several organizations collaborating on the investigation.

A version of Mr. Kuciak’s last, unfinished article, published on Wednesday by Aktuality and other news organizations, explored the business dealings of Antonino Vadala, an Italian man living in Slovakia whom the Italian authorities suspected of having ties to the ’Ndrangheta.

Mr. Vadala could not be reached for comment, and he is not quoted in the article.

The article’s publication prompted the resignation of high-ranking Slovak government officials. Mr. Kuciak’s report says the major investments that Mr. Vadala and his associates made included farmland, to draw European Union agricultural subsidies.