Gunmen have kidnapped at least 12 people, including two children, in a southern Mexican region where gangs have perpetrated a series of mass abductions, authorities said Friday.

The van that was used to transport the group was found burnt on a road between the hamlets of San Jeronimo and San Cristobal, Guerrero state security spokesman Roberto Alvarez said, citing witnesses.

He spoke of around 30 armed people who abducted ‘a group of between 12 and 14 people.’

Some of the relatives of the missing have received phone calls from kidnappers demanding ransom money.

The abduction may have been perpetrated by a criminal group known as Los Tequileros, Alvarez said.

The mass kidnapping took place in a region known as Tierra Caliente, or Hot Land, where 21 men were kidnapped in January and found alive days later. That same month, four teachers who had been kidnapped elsewhere were rescued, while another was found dead.

Another 21 people were kidnapped and later rescued by police in a cave in the same region in early 2015, and 13 suspects were arrested.

‘There has been a phenomenon in Tierra Caliente, which is a very poor, rural and isolated area, of mass kidnappings by members of organized crime who are doing business with this type of crime,’ Alvarez said.

Police have detained kidnappers, ‘but this phenomenon continues to defy the authorities,’ he said.

Such kidnappings show that gangs specializing in kidnappings are no longer targeting just wealthy victims in Mexico.

Officials at the state prosecutor's office say Los Tequileros are hired guns of the Guerreros Unidos drug cartel, which controls much of the opium poppy production and heroin smuggling in the region.

The cartel is also accused of colluding with local police who abducted 43 students in the city of Iguala in September 2014, a case that has drawn international condemnation.

Federal officials have said that Iguala police handed the students over to the cartel, which killed them and incinerated their bodies, though new lines of investigation have been opened after independent experts questioned the credibility of the case.