"At this stage, we do not believe that the murder is linked" to Marinova's work, Tsatsarov said.
Marinov said that Krasimirov, who is a resident of Ruse, had a criminal record for scrap metal theft and that there was physical evidence linking him to the crime scene.
Ms Marinova hosted a show last month featuring two investigative journalists who were detained for their work on suspected fraud involving European Union funds. The 30-year-old disappeared after going for a run and was found dead on Saturday in a park near Ruse.
Her final show on September 30 was about Attila Biro, an investigative journalist with the Rise Project Romania, and Dimitar Stoyanov from the Bulgarian investigative site Bivol.bg.
It is not clear if Marinova's murder was related to her journalistic work.
The attack has shocked the country and drawn global condemnation amid speculation the murder could be linked to Marinova's work as a journalist.More news: Watch Google's Pixel 3 Event Live Stream Right Here
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Maltese journalist Daphne Caruana Galizia was killed in a vehicle bomb in October.
However, Bulgarian Prime Minister Boyko Borisov lashed out at worldwide bodies and rights groups which had been quick to assume a political motive behind the murder. "In the frame of three days I read monstrous things about Bulgaria and none of which was true", he said.
European Commission vice president Frans Timmermans had been among the first to suspect a political motive.
The CPJ said it was "shocked by the barbaric murder".
Widespread corruption, shady media ownership and suspected collusion between journalists, politicians and oligarchs have made objective reporting a constant obstacle course, according to RSF. "Again a courageous journalist falls in the fight for truth and against corruption", he tweeted Sunday, not long after the news of the murder broke. His repeated attacks on the media's credibility and legitimacy have wide-ranging and risky implications for the safety of journalists and press freedom.
Bulgaria ranked 111 out of 180 countries in the Reporters Without Borders world press freedom index this year. "Bulgarian authorities must employ all efforts and resources to carry out an exhaustive inquiry and bring to justice those responsible", the media watchdog said in a statement.
Vigils in Marinova's memory were held Monday evening in Ruse, the capital Sofia and other cities.
"We call for police protection to be provided for the TVN journalists who worked with Viktoria Marinova on the same sensitive report, pending the outcome of the investigation", he added.