A group of masked gunmen kidnapped 31 migrants of different nationalities aboard a bus in Mexico over the weekend as they were traveling toward the border with Texas, Mexican authorities said.

The bus carrying 36 people was stopped on Saturday on the highway that connects the border cities of Reynosa and Matamoros, which sits across from Brownsville, Texas, Federal Security Secretary Rosa Icela Rodríguez said Wednesday.

The armed men forced all the migrants off the bus and abducted 31 of them in five vehicles, Rodríguez said. The abducted migrants were from Ecuador, Colombia, Venezuela, Honduras and Mexico.

She said that Mexican authorities are using technology to search for the kidnapped migrants.

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"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," Rodríguez said, according to Reuters.

Authorities have also reviewed surveillance video from the bus and scoured the area by helicopter, though have yet to find any signs of the missing.

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Rodríguez said the kidnapping was "atypical" because migrants are usually taken in small groups.

Organized crime groups that control the border area regularly kidnap migrants to hold them for ransom, with large abductions previously occurring in Tamaulipas state. 

In March 2019, 22 people were taken from a bus and not seen again. The Zetas cartel also massacred 72 Central American migrants who had been taken off buses near San Fernando, Tamaulipas in 2010.

The Associated Press contributed to this report.