Fears are growing for the health of kidnapped Colombian politician Ingrid Betancourt, prompting international appeals for her release by Farc rebels.
Ingrid Betancourt's family have waited six years for her release
Reports from four Colombian hostages released by the rebels on Wednesday suggest Ms Betancourt, who is also a French citizen, is seriously ill.
French President Nicolas Sarkozy says he is prepared to collect her himself.
The political hostages attract media attention, but the Farc is also holding hundreds of civilians for ransom.
'Near the end'
The four hostages released by Farc in a deal brokered by Venezuelan President Hugo Chavez were all members of Congress.
While they were tearfully reunited with their family and spoke of their ordeal in the Colombian jungle, the released hostages also spoke of Ms Betancourt's deteriorating health.
One, Luis Eladio Perez told reporters: "It hurts my soul, she is very bad, very, very sick. She is exhausted physically and in her morale.
"Ingrid is mistreated very badly, they have vented their anger on her, they have her chained up in inhumane conditions."
Another, Gloria Polanco, told President Chavez: "I ask you to fight for the release of Ingrid Betancourt really soon, she is very ill, president, very ill. She has recurrent Hepatitis B and is near the end."
After meeting Ms Polanco and her colleagues, Mr Chavez did make what he called an appeal "from the heart" to the Farc's leader to move Ms Betancourt to a safe location "while we continue working to pave the way for her definitive release".
Ms Betancourt was kidnapped in February 2002 along with her aide, Clara Rojas - who was released in another Chavez-brokered deal last month.
The last video of Ms Betancourt was released in November showing her looking extremely thin, sitting on a chair in the jungle, not speaking but just looking at the ground.
In a letter addressed to her mother released shortly after the video, she says her strength has diminished, her appetite has gone, and her hair is falling out.
Ms Betancourt's daughter, Melanie Delloye, told French RTL radio she hoped a humanitarian agreement would be reached as soon as possible.
"This is extremely worrying, and I know that time is really up for us," she said. "So mum is alive, but I don't know for how long, and I know that we need to get her out of there as soon as possible."
She said she hoped that the Farc guerrillas understood that "if they have hostages in really dangerous physical conditions, as is mum at the moment, they must not jeopardise their lives to the very end".
Mr Sarkozy joined the calls for Ms Betancourt's release, adding that he would be prepared to fetch her himself if that was a condition set by the Farc.
"This is a question of life and death," he said, during a trip to Africa. "They cannot leave this woman to die."
The Farc rebels, who have long wanted to exchange their high-profile hostages for hundreds of jailed guerrillas, say they will not free more hostages until Colombia creates a demilitarised zone for talks.
Colombian President Alvaro Uribe has maintained a firm stance against the Farc, which is regarded as a terrorist group by the US and the European Union.
The BBC's Jeremy McDermott in Medellin says that with the release, the pressure on Mr Uribe to make concessions to the Farc will increase.