Police in Slovakia have released seven Italians who were detained as suspects in the killing of an investigative journalist and his girlfriend.

The seven men had been taken into custody on Thursday when police raided houses allegedly linked to members of an Italian crime syndicate.

Police confirmed their release on Saturday but gave no details. The men range in age from 26 to 62. State prosecutors declined to comment.

The journalist Ján Kuciak and his partner, Martina Kušnírová, were found shot in their house on Sunday. Kuciak was working on a story about the influence of the Italian mafia in Slovakia and its possible ties to people close to the prime minister, Robert Fico.

Kuciak’s funeral is scheduled for later on Saturday.

The FBI, Scotland Yard and Europol are helping Slovak police with the investigation.