Colombia's main leftist rebel group, the Farc, has released another hostage, bringing the number of those freed this week to four.
Carlos Alberto Ocampo, a policeman captured six weeks ago, was handed over to a humanitarian delegation.
The release of two more hostages also scheduled for Sunday did not go ahead.
A government official said the rebels failed to turn up at the agreed co-ordinates for the handover, a move he described as "scandalous".
Government mediator Eduardo Pizarro Leon Gomez said the helicopters with the humanitarian delegation arrived at the agreed co-ordinates in Tolima province only to find the rebels had moved the hostages southwest to Cauca province.
"They moved them over the mountain range, which shows a strange attitude, one that annoys the government," Mr Pizarro added.
He said the government had done everything by the book and blamed the Farc for the failed handover.
But he did not rule out another attempt for Monday.
Piedad Cordoba, a former senator who has helped mediate the release, has asked President Juan Manuel Santos for permission to arrange a flight to a new location on Monday.
Mr Ocampo, 30, who was released at a separate set of co-ordinates in Tolima, has already been reunited with his family.
He was taken to an air base in Bogota, where he greeted his wife, two daughters and his parents wearing his police uniform.
Patrolman Ocampo was kidnapped in December 2010 while serving as a bodyguard for a local mayor in Tolima.
The mayor was released shortly after the kidnapping, but the Farc continued to hold Mr Ocampo.
He had not originally been on the list of the five hostages chosen for the unilateral release by the Farc, and news of his planned release were only made public on Saturday.
His wife had earlier told Colombian radio of her relief when she was able to speak to her husband shortly after he was freed.
"He sounded a little nervous, but happy, he told me he was well and that I shouldn't worry," she told Caracol Radio.
The Colombian government says the rebels still hold more than a dozen members of the security forces and scores of civilians and has made the release of all hostages a condition for peace talks with the rebels.