Mexico City ( CNN ) -- Traversing Mexico 's highways as a bus driver has always been a dangerous job , says Enrique , whose route takes him from central Mexico to Tamaulipas , on the border with the United States . `` But never like now , that I can assure you , '' said Enrique , who has been a driver for three years . His view coincided with other bus drivers who spoke with CNNMexico , who drive through drug cartel territory , and asked for anonymity because of fear of retribution for speaking on the record . Assaults , armed men , crossfire , bodies or human heads on the side of the road , form part of the daily stories that drivers have told each other in the past two years . It is a reality that came to light with the discovery last month of mass graves in the town of San Fernando , Tamaulipas , that possibly contained the bodies of kidnapped bus passengers . In addition to the development of kidnappings and assaults of passengers , bus drivers are extorted so that they may transit freely on the highways . `` In some places these people ( drug cartels ) ask for money in exchange for our security . ... They ask us for money to supposedly travel safely on the roads , '' said another bus driver . How much money do they demand ? `` From 200 to 1,000 pesos ( $ 17- $ 87 ) . '' What guarantees are there that with that they will leave you alone ? `` There is no guarantee , but there is nothing we can do when they arrive with a gun , intimidate you , and tell you they belong to this or that criminal group . '' `` Suddenly , on the street , they watch us , they arrive in trucks , it 's easy to recognize us because of the uniform , '' the driver continued . `` They approach and say , ' I come from this place and belong to this group . We are asking for your cooperation , or else there will be problems -- consequences . '' Carlos , a bus driver with 10 years of experience , said that in his travels through Tamaulipas , he has been witness to armed confrontations between police and traffickers , and in more than one occasion has seen bodies strewn or mutilated on the highways . One time , he had to maneuver his bus to avoid running over two groups who were firing on each other right on the highway . `` I accelerated and dodged the bullets , '' Carlos said . `` The passengers were scared . Some cried , others prayed . '' `` I almost ran over all of them because they passed by running . They did n't care about the size of the bus , or about who was on the highway , they crossed it in plain morning . We accelerated to avoid that a bullet would hit the bus , '' he added . In more than a decade of driving through the Tamaulipas cities of Reynosa , Matamoros , Ciudad Victoria and even San Fernando , Carlos said that he has never seen anything like what he has witnessed in the past months . `` Not even when we had to cross the mountains . Now , not even the highways are safe , '' he said . Another driver , referring to the kidnapping and apparent killing of bus passengers in San Fernando , said , `` We had been witnesses to the violence in the country . Today we are protagonists . It touched us , they reached us . '' Government analysts and the country 's National Human Rights Commission , posit that Tamaulipas , like other northern states , two phenomena have converged and resulted in the recent violence : drug trafficking and migration . The drivers interviewed agreed that the routes in the north part of the country have become desirable for criminals because a majority of the bus passengers are migrants destined for the United States . `` ( These are ) people who are carrying money or who comes from ( the United States ) with dollars and gifts for their families , '' the driver says . According to the human rights commission , last year more than 11,000 migrants were kidnapped in Mexico during their journeys to the United States . And , according to the National Security System , in 2010 there were 2,142 robberies on highways in all of Mexico . States like Michoacan and Tamaulipas went from having zero highway assaults last year to 11 and 28 , respectively , so far this year . `` There were always assaults on the highways , but they were sporadic and another type of crime . They were people dedicated to robbery , but not drug trafficking , '' said another bus driver , who identified himself as Rafael . `` We ca n't explain what is happening . We suppose that it is the reaction of organized crime to the job the government is doing to eliminate them , but at the same time we see a lot of corruption among the police , '' he said. `` The cities of Matamoros , Reynosa and Laredo , in the northeast of the country , are the considered the most dangerous routes . Asked if they want to continue traveling north , a bus driver answers that , `` for necessity , for work , by orders , but it is unsafe . In a tone of jest they ask us if we are carrying our bulletproof vest and helmet . Once someone tells you that , you start thinking , ' I hope nothing goes wrong . ' ''
Buses traveling through northeast Mexico face dangerous situations . Bus drivers report assaults , crossfire and finding bodies . Criminals extort them in exchange for safe passage .