The Mexican army freed 61 migrants discovered inside a safe house in the northern border city of Reynosa, the government said Thursday.

The majority of the captives were Central American migrants trying to reach the United States, Mexico's security forces said in a joint statement.

The rescue operation unfolded Wednesday afternoon after soldiers on patrol heard cries for help from inside a home in the Sierra de la Soledad neighborhood of Reynosa, which lies just across the border from McAllen, Texas.

Once inside the house, the troops found 33 Guatemalans, 20 Salvadorans, four Hondurans, one Nicaraguan and three Mexicans, the statement said.

The captives told authorities they had been held for 15 days by migrant-traffickers who were demanding payments of up to $6,000 each to bring them into the United States.

Hundreds of thousands of Central Americans undertake the hazardous journey across Mexico each year on their way to the United States. The trek is a dangerous one, with criminals and corrupt Mexican officials preying on the migrants.

Gangs kidnap, exploit and murder migrants, who are often targeted in extortion schemes, Mexican authorities say. EFE