MEXICO CITY (Reuters) -Mexican authorities are tracing phone signals as they intensify their search for the 31 migrants kidnapped in the northern Tamaulipas state, underscoring the peril facing people crossing Mexico's crime-ridden regions to reach the United States.

       Unknown gunmen on Saturday snatched the mostly Latin American migrants from a bus on a highway in the municipality of Reynosa, close to the border from the United States. The bus was destined for Matamoros, across from Brownsville, Texas.

       Asylum seekers and human rights activists have for months been warning of an escalating kidnapping crisis in the Tamaulipas border region, especially in Reynosa, where various powerful criminal groups jockey for power.

       Mexican Security Minister Rosa Rodriguez said on Wednesday that the kidnapped migrants were from Venezuela, Ecuador, Colombia, Honduras and Mexico.

       "Several actions have been carried out, among them, the tracking of the phones to locate the people who carried out (the kidnapping) and find those responsible for this crime," said Rodriguez.

       "We hope to quickly find the location of the victims," she added.

       Colombian President Gustavo Petro on Tuesday said on X, formerly Twitter, that four Colombians were among the kidnapped migrants and the country's embassy was coordinating with the Mexican government for them to be rescued safely.

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       Rodriguez said the kidnapping was "unusual" due to the large number of victims, though it's not uncommon for migrants to be pulled off buses and kidnapped in Mexico. Usually, the migrants are forced to beg their relatives to pay ransom money.

       In March 2019, armed men stopped a passenger bus on the San Fernando-Reynosa highway and kidnapped about 20 people. To date, their whereabouts are unknown.

       In May last year, 49 migrants, including 11 minors, were released after being kidnapped in the south of Mexico while traveling by bus to the U.S. border.

       A record number of migrants traveled across Central America and Mexico in 2023 aiming to reach the United States, fleeing poverty, violence, climate change, and conflict.

       (Reporting by Stefanie Eschenbacher and Diego Ore;Editing by Drazen Jorgic and Bill Berkrot)