Paper: Murder probe opens after Jefferson City man disappears in Siberia
The Siberian Times said a preliminary check by Russia's equivilant of the FBI indicates there may have been foul play.
The paper quotes a statement from the Investigative Committee as saying no hard evidence and no body has been found, but "established facts indicate that a crime may have been committed against him."
The guest house where Madsen was staying has been checked for blood, the paper quotes a friend of Madsen as saying.
A local TV channel said three friends of Madsen are believed to have been questioned, including American Lucas Fagre, who did an online interview with KOMU 8 News Tuesday.
At that time, Fagre said Madsen went for a walk around 3 a.m. Sunday, which he often did, but this time he did not return.
"On the one hand, it seems kind of like him, for him to just leave like that, but I dont know, just a lot of things are off," Fagre told KOMU 8 News.
Fagre said he, Madsen and two of their Russian friends were on a trip to Arshan, a tourist destination, to hike a mountain.
NBC News reported Madsen went missing wearing only a T-shirt in subzero temperatures.
Search crews are using drones and a large volunteer force to search for Madsen, according to the Siberian Times.
Arigus TV said, "Half of the local residents of the village are also involved in the search for the missing tourist. Mountains National Park combing the staff and rescuers. The situation is aggravated incessant snow."
The TV station quoted a volunteer as saying the snow in the search area is knee-deep and there has been no trace of Madsen.
His mother, Dana Calcutt, is now in Arshan village with the investigators, the Siberian Times reports. She is in Russia on a "victim status" visa, according to Arigus TV.
Madsen's stepfather, Michael Calcutt sent KOMU 8 News an email Thursday saying, "We are very grateful to the State Department and the Russian consulates/embassies for working to grant emergency travel documents."
Calcutt said the family has heard nothing except what's being reported online.
"We are encouraged to learn that the local authorities have stepped up their search," he said.
Madsen was from Jefferson City and studying at Irkutsk State Linguistic University in Siberia.