Félix survived his ordeal at the hands of the Zeta cartel, one of Mexico's most ruthless drugs gangs. But he knows of many fellow migrants who suffered the same grisly fate as the 72 who were shot at an isolated ranch 70 miles from the border city of Reynosa.

"There are lots more dead migrants, they just haven't found them," says the 20-year-old Honduran, speaking at a shelter for migrants run by nuns in Reynosa.

Unlike those at the ranch who were travelling in one large group and kidnapped by an armed commando, Félix (whose name has been changed) was alone when he was picked up by a policeman. In an example of the official collusion that human rights activists have long claimed endangers migrants in Mexico, the officer took him to a Zeta safe house and left him there.

For a week he was a side-show for gunmen who beat him with planks and pistol handles and gave him electric shocks to intensify his screams when they put him on the phone to his poverty-stricken family, demanding money for his release. The rest of the time, he says, he was forced to watch his captors going about the more serious business of torturing information out of captured members of the Gulf cartel by cutting off different pieces of their bodies each day for about a week. Then they were killed, their mutilated bodies burnt to dust on the mountainside.

"They told me the same thing would happen to me, if the ransom didn't arrive," he says.

Félix's father in Honduras and brother in Atlanta managed to raised $5,000 and wired it to Mexico. The Zetas demanded as much again and his family stopped answering the phone.

During his two-month ordeal Félix says he was moved to six different safe houses. In one he was crammed into a swelteringly hot small room with 80 other migrants. In another there were 120. Every day they were taken out individually to be beaten.

"Sometimes I couldn't think of anything because of the pain," Félix says. "Other times I would just sit there wondering how people could be that bad." Every week, he says, about five migrants whose families had paid nothing were taken away. He assumes they were killed and their bodies destroyed.

He was offered his life in exchange for 12 weeks' intensive training in the use of heavy weapons in a jungle camp and a monthly salary of $5,000. After that, his captors said, he would be a member of the cartel with money to burn. Desperation prompted him to ask if he would be allowed to see his family again, but they said no: "They told me that the only way out of being a Zeta was death or jail."

Amazingly, he was spared. Dumped in Reynosa unable to walk and with his face so swollen he could hardly talk, somebody took him to the shelter. That was five months ago. Now he no longer vomits blood and his bruises have faded but he lives in limbo. He is reluctant to get himself deported to Honduras, where he feels he has no future, but too scared to try to cross illegally the US border, even if he had the money to pay a smuggler to show him the way. Many smugglers are linked to the cartels.

He doesn't dare go out into the streets of Reynosa, because he is terrified of roaming kidnappers and the battles that periodically break out on the streets between the Zetas, the Gulf cartel and the military. In April, gunmen with "Gulf cartel" printed on their bulletproof jackets broke into the building where Félix is staying and lined everybody up against the wall. When they didn't find who they were looking for they left.

Sister Ligia, one of the nuns at the shelter loses her habitual sprightliness for a moment: "That massacre at the ranch. That's just the tip of the iceberg."