Colombian officials said Thursday that Marxist rebel group, the National Liberation Army, or the ELN, was responsible for the kidnapping of three journalists near the country’s border with Venezuela, media reports said.

Defense Minister Luis Carlos Villegas said intelligence reports “confirm with certainty” that the rebel group was responsible for the disappearance of the journalists. “From this point on the responsibility for the safety and freedom of these three citizens is exclusively in their hands,” he added, according to the Associated Press.

Spanish reporter Salud Hernandez-Mora, 59, was the first to disappear after she was last seen climbing aboard a motorcycle taxi Saturday. Hernandez-Mora was reportedly working on a story about illegal drug trade in the Catatumbo region near the border.

Reporter Diego D'Pablos and cameraman Carlos Melo of local television channel RCN were the other two journalists to go missing. The two were covering the search for the Spanish journalist when they disappeared Tuesday.

RCN News Director Claudia Gurisatti told CNN Tuesday that a government human rights official first confirmed the disappearance of her network's journalists.

“They called us and said that, ironically, the group of journalists who were covering what people in the area knew about Salud's disappearance had themselves been attacked. Their belongings, including their equipment, cameras, computers, communication equipment, telephones, were taken from them,” Gurisatti said.

President Juan Manuel Santos Wednesday had held out the possibility that Hernandez-Mora hadn't returned as she might have chosen to report from inside of a rebel camp. However, the government later issued a statement calling for the immediate release of the missing journalists.

According to Reuters, even though Colombia and the ELN agreed in March to begin peace talks, Santos said at the time that no official talks would begin until the group freed all hostages.

The rebel group has not commented on the situation, reports said.

Hernandez-Mora writes for the Spanish daily newspaper El Mundo and is known for opinion columns highly critical of Colombia's insurgents, the Santos administration and the peace process.