(CNN) -- The trek for those traveling through northern Mexico remains dangerous: police rescued 73 people who were being held hostage in the border city of Reynosa.
The victims had been kidnapped from buses or bus terminals, and about half were Central Americans, police said. It is likely, though police did not say, that a majority of the victims were migrants on their way north to the United States.
Some of the kidnap victims were held for as long as four months, Mexico's National Security Commission said in a statement.
Federal police on patrol Monday in Reynosa followed a car after its occupants tried to avoid them, the commission said. When the two men in the car pulled up to a house, so did the police.
The police approached the house "from where they could hear cries for help," the commission said.
Inside the house, police found 73 hostages: 37 Mexicans, 19 Hondurans, 14 Guatemalans, and three Salvadorans, it said.
Six minors were among those rescued, the commission said.
The victims told police that some had been held between four days and four months. The alleged kidnappers made phone calls to the victims' families, demanding ransom payments in exchange for their release, the commission said.
Some of the people rescued said they were assaulted or raped, it said.
Police arrested the two men in the car who arrived at the house, and a third man who they allege worked as a lookout.
Authorities have discovered at least three mass kidnapping operations in and around Reynosa this year. In July, Mexican authorities rescued 81 migrants they said were held captive in Reynosa.
And in June, authorities said that in a small town nearby they rescued 165 migrants who were kidnapped as they tried to cross into the United States.
The dangers are not limited to the north of the country.
In July, authorities in southern state of Chiapas rescued 94 migrants who were crammed into the back of a hauling truck in "subhuman conditions."
They showed symptoms of asphyxiation and serious lesions on their hands and feet when they were rescued.