"The number of people, mainly adults but including children, reported trafficked from Vietnam to Scotland continues to rise," Detective Superintendent Filippo Capaldi, head of the Scotland police’s national human trafficking unit, said.

"Many of these people will have come to Scotland, and the U.K., under false promises of a better life, only to find themselves victims of exploitation by criminal gangs."

This year 397 referrals have been received by the unit, half about Vietnamese victims, 90 of them ostensibly minors.

It represents a 20 percent increase from last year.

The victims of trafficking or smuggling usually do not contact the police directly but come to their attention in other ways.

"One of them is to be reported to the police by either members of the public or other agencies," Brenda Irons-Roberts, a communications officer in the police department, said.

She declined to discuss details about individuals with whom the police are dealing since they are potential victims of trafficking by criminal gangs and there could be risks associated with this.

Capaldi said a number of initiatives are being developed with his unit's partners to ensure that when potential victims are identified they receive the support they need.

"This includes ensuring any children identified are protected and receive the full support of Scotland's well-developed child protection."

The majority are trafficked for forced labor, according to the U.K. National Referral Mechanism, which identifies potential victims of modern slavery and ensures they receive the appropriate support.

Information about the elite squad comes a few weeks after the tragedy in which 39 Vietnamese people were found dead in the back of a truck near London. The youngest victims were 15.

While trafficking of Vietnamese to the U.K. is not new, the rise in their number in Scotland makes sense from a business viewpoint for organized crime, according to Mimi Vu, a Vietnam-based independent anti-trafficking expert.

"The market for cannabis cultivation and smuggling of migrants is more saturated in the southern part of the U.K. In order to expand their business and respond to the increased attention being paid by law enforcement in areas around Kent, London or Essex, for example, traffickers and criminal gangs have spread their activities to farther-flung places like Scotland."

But she is wary of Scotland's lack of capacity in working with Vietnamese victims. When she visited Glasgow last year to meet with the police, government officials and non-governmental organizations for her work, there were only two qualified Vietnamese translators in all of Scotland.

"The police and NGOs don't have any experience in dealing with Vietnamese at all."

She said Scotland needs to train its law enforcement and social services to understand the Vietnamese cultural context in which the potential victims are brought, particularly minors.

"Otherwise they will have the same situation of Vietnamese minors going missing in care and returning to their traffickers as they do in the rest of the U.K."

British ambassador to Vietnam, Gareth Ward, vowed action against human trafficking as he expressed his condolences to families of the U.K. truck victims on Wednesday, when the first bodies of the victims arrived home.