She was discovered near a pedestrian alley in an area with heavy vegetation, according to Bulgarian state media, and initial investigations indicate her cause of death was blows to the head and suffocation.
Interior Minister Mladen Marinov said today that there is no evidence to suggest the killing was linked to Ms Marinova's work.
Bulgaria's prosecutor general, Sotir Tsatsarov, confirmed the arrest of Severin Krassimirov, a 21-year-old Bulgarian citizen.
The first episode of Marinova's program aired September 30 and featured two investigative journalists - Dimitar Stoyanov from the Bivol.bg website and Attila Biro from the Romanian Rise Project - discussing their investigation into allegations of fraud involving European Union funds linked to prominent businessmen and politicians in Bulgaria.
Bulgarian police questioned a Romanian man about the murder of TV journalist Viktoria Marinova on Tuesday but released him without charge and the country remains under worldwide pressure to solve the crime. He tweeted: "Again a courageous journalist falls in the fight for truth and against corruption".
Police and prosecutors are investigating the death of 30-year-old Viktoria Marinova, who hosted a show on the regional TVN channel.
Margaritis Schinas, spokesman for European Commission President Jean-Claude Juncker, said Monday that the commission expected "a swift and thorough investigation. that will bring those responsible to justice and clarify whether this attack was linked to her work".
"The evidence that we have at this stage leads us to believe it was a spontaneous attack to sexually abuse the victim".
"I will closely follow the investigation opened by the authorities".More news: North Korean leader Kim Jong Un expected to visit Russian Federation soon
And even some of Marinova's fellow journalists were not convinced that she was killed because of her reporting.
Local media focused on Marinova's recent TV interview with Bulgarian journalists Attila Biro and Dimitar Stoyanov who were investigating alleged large-scale fraud by companies involved in EU-funded infrastructure projects.
Mourning vigils are to be held in Sofia and other cities on the evening of October 8 for Viktoria Marinova, a journalist for a Rousse cable television station, found murdered in the Danube city this past weekend.
The country's Prime Minister Boyko Borisov is confident that Marinova's killer would be apprehended and brought to justice, adding that the "best criminologists were sent to Ruse" and "a large amount of DNA has been obtained".
They did not offer any new details about the case after their meeting with the local authorities.
Ms Marinova is the third journalist to have been murdered in the European Union in a year.
Worldwide, at least 48 journalists have been killed doing their work in 2018, according to the Committee to Protect Journalists, an advocacy group that does an annual count of detained and killed journalists.
Through a United Nations spokesperson, Secretary-General António Guterres called on "all governments to strengthen press freedom and ensure there is accountability for crimes committed against journalists".
Bulgaria was the lowest-ranking European Union member in Reporters Without Borders' 2018 World Press Freedom Index.