By Jeremy McDermott
BBC News, Medellin
Exhumation of bodies has shed light on the alleged atrocities
The toxic fallout of a grisly army scandal continues to spread in Colombia, as more soldiers are arrested over their alleged roles.
In recent days another three colonels have been arrested, bringing the total number of military personnel captured to at least 22.
The "false positives" scandal has revealed that the army murdered civilians, who were then dressed in rebel uniforms or given guns. They were then presented as guerrillas or paramilitaries killed in combat.
These allowed units to fabricate results, and officers to gain promotion.
The number of victims is believed to be in the thousands.
"The issue of the false positives puts into doubt the doctrine of the security forces with respect to human rights," said Maria Victoria Llorente, director of the think-tank Foundation Idea for Peace. "This puts at risk a prized value for the military: legitimacy."
Demand for results
By certain measures, the "democratic security" policy of President Alvaro Uribe has been a great success. It has pushed back Marxist rebels from around the cities and deep into their mountain and jungle strongholds.
It has demobilised 30,000 members of an illegal right-wing paramilitary army, the United Self Defence Forces of Colombia.
It has seen a massive drop in kidnapping and a fall in the murder rate, once among the highest in the world.
But Mr Uribe's demand for results has pushed his security forces to the limit - and this appears to have provoked this scandal of the false positives.
The scandal broke last October when it was found that poor, young men had been recruited from the slums of Bogota, promised well-paying jobs in the province of Norte de Santander, then murdered in cold blood and presented by the army as having been killed in combat.
The attorney general's office has evidence that 30 young men were murdered in such circumstances, and so far 17 soldiers have been arrested in connection with these extrajudicial killings.
The funding for these operations allegedly came from the budget for informants. The paying of informants is one of the central struts of the democratic security policy.
However, more examples of false positives are coming to light, spread across the country. Prosecutors now have 900 cases on their books, involving 1,500 victims, with more reports arriving daily.
Sixty-seven soldiers have already been found guilty and more than 400 have been arrested and are awaiting trial.
A total of 1,177 members of the security forces are currently under investigation linked with cases of extrajudicial killings.
Here in Antioquia province, where the most cases have been reported, the attorney general's office is investigating Battalion Bombon.
It is alleged that soldiers were sent to the city of Medellin to round up homeless people from the streets who were later presented by the army as rebels killed in combat.
Investigators have managed to identify six cases, and 46 operations by the battalion are being scrutinised amid fears that they were simply staged using murdered civilians.
Mr Uribe's democratic security policy has demanded results from the army
The most recent case of a false positive took place in the northern province of Cordoba in December last year, which was well after 27 soldiers, among them three generals and 11 colonels, were sacked as part of the scandal.
Defence Minister Santos, who is likely to run for the presidency in 2010, then stated that the problems had been resolved and that the human rights abuses would be stopped.
However last week he admitted that a student, Arnobis Negrete Villadiego, had been snatched off the streets of Monteria in Cordoba on Christmas Day.
The corpse of the 18-year-old appeared a day later, presented as a member of a drug-trafficking gang killed in combat.
But the minister insists that the situation is not as bad as the media is making out.
"We have discovered that there are many false denunciations, many people that want to present legitimate killings in combat, terrorists, guerrillas, as extrajudicial executions, in order to stain the good name of our military institutions," said Mr Santos.
President Uribe has said the same thing, insisting that elements linked to the guerrillas are using the false positives to undermine military morale.
"We have to be the first to denounce that many people, using the [false positives scandal], have made false accusations, to try to paralyse the action of the security forces against the terrorists," the president declared.
The scandal is having international implications.
The British government has now diverted part of its aid to the Colombian military to other programmes that could have no links to the false positives, explained Alan Campbell, of the UK's Home Office, who visited Bogota this week.
The White House is also studying the aid package known as Plan Colombia, which has delivered more than $6bn (£4bn) in mainly military aid since 1999.
Sources in the US embassy in Bogota said that it is likely to be cut, or at best have funding directed away from the military and into social investment programmes.