Colombian security forces have launched an operation to find a missing Spanish reporter who may have been kidnapped, President Juan Manuel Santos says.
Salud Hernandez Mora, from the El Mundo and El Tiempo newspapers, was last seen on Saturday in north-eastern Colombia, where she was investigating coca crops.
Spain's foreign ministry said it was unclear whether she had been kidnapped.
They had earlier said they suspected rebel group ELN to be behind her disappearance.
The ELN is the second-largest guerrilla group in the country, after Farc.
President Santos said: "I have told the security forces, our generals, commanders and the chief of police to deploy all forces necessary to find her and free her if she is being held."
'Detained by guerrillas'
Ms Hernandez Mora has been a correspondent in Colombia for nearly two decades. She has dual Spanish and Colombian nationality.
El Tiempo (in Spanish) said she had been investigating the eradication of coca crops when she went missing.
The region Ms Hernandez Mora was in is known to have a presence of left-wing guerrilla groups and criminal gangs that profit from drug trafficking.
About 220,000 people have died in the conflict in Colombia, which started in the 1960s. A further 45,000 are missing, while 6.6 million people have had to leave their homes.
The Colombian government has entered into peace negotiations with the ELN, which is estimated to have about 1,300 members.
Farc which has about 7,000 members, has been in talks with the government since 2012 and it is expected an agreement will be formally signed by the end of 2016.
Colombia is one of the most dangerous places in the world for journalists, who face intimidation from drug traffickers, guerrillas and paramilitaries.
Who are the ELN rebels?
- The group was founded in 1964 to fight Colombia's unequal distribution of land and riches. It was inspired by the Cuban revolution of 1959.
- One of its key leaders was Camilo Torres, a priest and pioneer of liberation theology, a radical movement within the Catholic Church especially popular in Latin America, where it emerged in response to widespread poverty and ill-treatment of ordinary people.
- The rebel group was created in the 1960s to fight Colombia's unequal distribution of land and riches.
- Over the decades, the guerrilla group has attacked large landholders and multinational companies and has repeatedly blown up oil pipelines.
- To finance itself it has resorted to extortion, kidnappings and drug trafficking.
- The ELN has been strongest in rural areas.