This undated photo, courtesy of El Tiempo newspaper, shows Salud Hernandez-Mora, correspondent in Colombia for Spain's El Mundo and columnist for the Bogota daily El Tiempo, working in an unknown location in Colombia. Security forces are searching for Hernandez-Mora, who was last seen on Saturday, May 21, 2016 in El Tarra, on the northeastern Colombia's border with Venezuela, a mountainous area dominated by leftist rebels and drug-traffickers. (El Tiempo via AP)

BOGOTA - Two more journalists were reported missing Tuesday in a lawless region where Colombian security forces were already carrying out an extensive search for a prominent Spanish journalist who disappeared over the weekend.

The two journalists from the right-leaning TV network RCN had travelled to the Catatumbo region to cover the hunt for Salud Hernandez-Mora, a longtime correspondent for the Spanish newspaper El Mundo whose weekly column in the Bogota daily El Tiempo is one of the most read in Colombia.

Authorities declined to call Hernandez-Mora's disappearance a kidnapping, and no one had claimed responsibility for her disappearance, but speculation heightened that she could have been taken hostage by the rebel National Liberation Army, the ELN. It is one of several armed groups and drug trafficking gangs dominant in the mountainous area bordering Venezuela.

Journalists from the Spanish news agency EFE and local network Caracol were detained briefly by armed men Monday covering the search. Diego Velosa from Caracol said he was stopped by a group identifying themselves as members of the ELN and forced to hand over equipment during a tense standoff that lasted a few hours. He said he was told by his captors that they were also holding RCN journalist Diego D'Pablos and his cameraman Carlos Melo.

Hernandez-Mora had not been seen or heard from since Saturday, when she was spotted arguing with an unidentified man and then hiring a motorcycle to take her to an unknown destination.

Pressure was mounting on President Juan Manuel Santos, who is struggling to maintain support for peace talks with the Colombia's two rebel groups, who Colombians overwhelmingly despise. On Tuesday, he ordered the head of the police and army to travel to Catatumbo to oversee the search.

Gen. Alberto Mejia, the army chief, said security forces face a steep challenge.

"We're not talking about a soccer field, we're talking about one of the most-difficult regions for the armed forces to operate," Mejia said at a news conference.

The Jamaica-sized region of northeastern Colombia is among the country's poorest, most marginalized backwaters. It is a major coca-growing area and corridor for cocaine smuggling to Venezuela, with the state able to maintain only a few militarized strongholds.

The region was home to a ruthless cocaine warlord and ex-rebel nicknamed "Megateo," until security forces finally tracked him down last year and killed him in an airstrike. Remnants of his Popular Liberation Army are still active in the area as is the ELN and the country's main rebel movement, the Revolutionary Armed Forces of Colombia, the FARC.

Santos has staked presidency on securing a deal to end Colombia's half-century conflict. While a deal with the FARC is near, talks with the ELN announced in March have barely gotten off the ground due to Santos' demand for the release of all captives held by the group, which relies on kidnapping to fund its insurgency. The ELN has said it didn't enter peace talks to discuss its tactics but rather put an end to the bloody conflict once and for all.

"It would be a joke for the ELN to continue talking about peace if it continues violating the most basic rules of warfare," Jose Miguel Vivanco, the Americas director at Human Rights Watch, said in a statement.

Conservative critics, among them Hernandez-Mora, have said that any deal is bound to fall short of expectations so long as vast stretches of rural areas remain ungovernable and effectively under the control of heavily armed illegal groups.

Hernandez-Mora, who has lived in Bogota since the 1990s and also has Colombian citizenship, is one of the South American nation's most influential journalists. Admired and reviled in equal measure for her opinion columns frequently critical of the Santos government's peace efforts, even her detractors in the government acknowledge her courageous reporting in violent areas where the state has almost no presence.

"Salud in the last five and a half, almost six years, has been a ferocious critic of my government," Santos said at a military ceremony Monday. "But precisely because she's a person who is critical of my government I've given the instructions to our security forces, our generals and commanders of all the security forces and the police, so they don't spare any effort in locating her and returning her to freedom if she is detained against her will."

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Associated Press writer Cesar Garcia contributed to this report.

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Joshua Goodman is on Twitter at https://twitter.com/apjoshgoodman . His work can be found at http://bigstory.ap.org/journalist/joshua-goodman .

News from © The Associated Press, 2016