By Nick Caistor
Regional analyst, Para state, Brazil
On a recent trip to several African countries, Brazil's President Inacio Lula da Silva made a point of apologising for historical slavery in his country.
Brazil was the last country in the Americas to abolish slavery, in 1888, just before it became an independent republic.
The workers are properly looked after, ranch owners say
Before that, for more than 350 years, African slaves had been shipped in their millions to work on sugar plantations and other large agricultural estates or fazendas.
Modern-day Brazil is plagued with similar practices.
These modern slaves are to be found mostly in the vast Amazon region of the north of the country, which is still frontier territory that the state cannot always control or police properly.
The workers are taken on by a gato, or gangmaster, usually to clear areas of the jungle which are then claimed, and eventually become part of huge cattle farms, after all the timber has been stripped out.
When he came to power in 2002, President Lula pledged to abolish these near-slave conditions in his own country.
He spoke in particular of Para state in Amazonia, where he estimated that some 10,000 of a possible national total of about 25,000 people were being forced to work in this inhuman way.
His government, and the federal police in particular, declared war on the cattle ranchers, or fazendeiros, who employed workers in these conditions, and promised to end the kind of impunity which has meant that few people are ever prosecuted.
At first, the mobile units of the labour ministry, accompanied by the federal police who swooped on any area where there were reports of slave labour, did reduce the number of denunciations, but there are signs that the practice is increasing again.
Regivaldo Pereira dos Santos, 22 years old, from the town of Redencao in Para state, won his court case against a fazendeiro, with the help of a human rights lawyer.
However, as he explained to BBC News, he has not yet received compensation.
"The gato took us upriver for several days in a boat. Then we were dropped off, and told to clear the forest. We only had a rough shack to live in and just the food we'd brought.
"The gato said he'd be back in a couple of weeks but he never appeared. There was no way we could get out of there because it was so isolated.
"After six months, the rains came and our shack was flooded. Eventually, we managed to get help and escaped. But we haven't yet got compensation, because it turns out that the fazendeiro didn't have rights to the land."
The cattle ranchers of Para deny there is any such thing as slavery in the region.
They argue that the workers are not forced to go, are nearly always properly looked after, and the proof of this is that many of them come back time and again looking for this kind of work.
Fernando Coimbra, who owns a large cattle ranch outside Redencao, insists that if abuses do occur, it is only a tiny majority of landowners who commit them.
But Frei Henri des Roziers, a French Dominican who has worked in the region for more than 30 years and has frequently received death threats from landowners, says this is not enough.
"If they think that only a small minority is committing this kind of crime, why do they not denounce these people openly - I've never heard any of the landowner organisations saying anything of the sort."
For Frei Henri, modern-day slavery is as clear cut as its historical predecessor.
"If these workers have no possibility of leaving, if they are prevented from doing so by armed guards, if they live in miserable conditions, and if they are charged more than they earn, then that to me is slavery," he says.
"And they return to these jobs because there is absolutely nothing else they can do in the region," insists the friar.
Alison Sutton, author of a book on slavery in Brazil who now works for Unicef in the capital Brasilia, agrees that the real solution is to provide more employment and better education for rural workers.
This hasn't yet happened, she says, but even so the Lula government has made important advances:
"They've drawn up a National Action Plan, bringing together all the initiatives, so that all bodies are co-ordinated and working together. Brazil also had a co-operation agreement with the International Labour Organization, which has involved a series of training seminars for judges.
"The whole issue has become far more public. It's discussed in the press, and there's an advertising campaign on television. Public awareness is much higher, and that's a big advance."