ASEAN KEY DESTINATIONS
EU's crackdown on Vietnamese illegals
With Hungary, Slovakia and the Czech Republic now all part of the Schengen group of countries, which have no border controls between them, migrants can reach the English Channel before being asked to show documents.
Some enter Schengen countries legally, on short-stay visas. Others cross illegally into Eastern Europe overland from Russia and Ukraine.
Historically close ties between Eastern Europe and southeast Asian countries have created better conditions for the smugglers, according to Andy Baker, deputy head of the Serious Organised Crime Agency in Britain, who visited Hungary this week.
"They may have a better footprint for safe houses and people who can look after them - hence the number of facilitators who were arrested in Hungary who are of Vietnamese and Hungarian background. This isn't just about Vietnamese organised crime," Mr. Baker told the BBC.
Police sources say most of the Vietnamese come from Haiphong, or from an area north of Hanoi.
There are 30,000 Vietnamese living legally in Britain, but police estimates put the illegal numbers at another 35,000.
There are 4,000-5,000 Vietnamese living in Hungary, according to Zoltan Baross of the National Bureau of Investigation. Many arrive in groups, with letters of invitation from non-existent companies. Of 900 Vietnamese who arrived recently in Hungary, 600 subsequently disappeared.
Police in both countries say that illegal migration is closely tied to cannabis production.
"We uncovered 40 cannabis plantations in Budapest in the last year - and in almost all of them we found Vietnamese working," said Mr Boross.
In Britain, more than 3,000 cannabis plantations were found by police in the same period, again with a strong Vietnamese connection, Mr. Baker said.
Using special lighting to produce three crops a year, each could generate profits of 1m euros (£820,870) a year, police estimate.