The armed men who kidnapped 32 migrants in northern Mexico over the weekend aimed to extort money from them and their families in the United States, Mexico's president said on Thursday, one day after the migrants were released from captivity, Paralel.Az reports citing Reuters.

He said that the migrants, who were found on Wednesday, were abandoned by their kidnappers in a parking lot in a shopping center in the northern city of Reynosa in the state of Tamaulipas.

"Because there was a strong deployment (from Mexican authorities), they decided to free them, safe and sound," President Andres Manuel Lopez Obrador said in his morning press conference.

The case has highlighted the risks faced by the hundreds of thousands of migrants who cross through Mexico en route to the U.S. border each year, who are targets of extortion and kidnapping by powerful criminal groups.

Human rights activists have been warning for months about an escalating kidnapping crisis in Reynosa, where last year Reuters documented a pattern of kidnappings - and at times sexual assault - of migrants and asylum seekers.

The 32 migrants were abducted on Saturday from a commercial bus that had departed the northern city of Monterrey for Matamoros, across from Brownsville, Texas, according to Mexican officials. They were forced off the bus while traveling through Reynosa and whisked away in cars by armed men, officials added.

In a separate case, authorities in the border state of Sonora said on Thursday they had rescued around 20 migrants, many also kidnapped off busses.