A police officer inspects an illegal cannabis farm in the U.K. in 2018. Photo by Reuters.

They raided a property in the town of Rochdale in the north of England on October 14 this year and discovered a large cannabis farm with an estimated street value of £850,000 ($1 million), the Greater Manchester Police (GMP) said in a statement on its website.

Upon discovery, officers found the three Vietnamese teenagers, whose name and gender have not been revealed, who were being criminally exploited to farm the illegal cannabis plants.

Initial investigations have revealed that the three children had been trafficked from Vietnam into the U.K., but no information has been released on how it had been done.

They were found to be living in squalid conditions with just three mattresses on the floor for them to sleep on.

"The children had been living at the cannabis farm for a number of months and it is believed that measures were put in place by those exploiting the children to ensure they were unable to leave the premises in case they raised any suspicions," said a spokesperson of GMP.

The children are currently being supported by specially-trained officers from GMP’s Child Criminal Exploitation team with the assistance of Children’s Social Care in Rochdale.

No arrests have been made and police are investigating the case to identify those responsible for producing the cannabis and exploiting the three children.

More than 3,100 Vietnamese adults and children were identified as potential trafficking victims by the U.K. government between 2009 and 2018, according to a report by Anti-Slavery International, ECPAT U.K. and Pacific Links Foundation.

Victims trafficked from Vietnam most commonly end up being exploited, often in cannabis farms and nail bars, but many are also sexually exploited, according to a report commissioned by Britain’s Independent Anti-Slavery Commissioner Kevin Hyland.

VNF ( Vnexpress )