Police investigating the activities of gangmasters suspected of employing illegal immigrant workers have arrested 40 people.
Police raided a house in Norfolk
The arrests were made after a series of early morning swoops across the UK, Norfolk police said on Thursday.
Ten men and 28 women were held in Scotland and two men in Norfolk.
A Private Members' Bill to license gangmasters has won MPs' support since 20 Chinese cockle-pickers died at Morecambe Bay, Lancashire, in February.
Norfolk police said six people had been arrested on suspicion of facilitating the entry of illegal immigrants into the UK and on suspicion of
Two of those were in King's Lynn, Norfolk, and the remaining four were driving two minibuses of workers stopped by police in Grampian, Scotland.
Two guns have been recovered from addresses searched in Norfolk, as well as substantial amounts of forged documentation and cash, a police spokeswoman said.
The co-ordinated raids - codenamed Operation Absent - involved officers from the Norfolk, Grampian, Cambridgeshire and Metropolitan police forces as well as the Immigration Service.
A van was stopped and checked as part of the Aberdeen raids
A spokesman for Norfolk police said: "The operation was to tackle the exploitation and influx of illegal
immigrants into the UK."
Those arrested are thought to include two Ukrainian men from King's Lynn.
A Grampian Police spokesman said 70 of the force's officers had been involved in the operation, in partnership with the Immigration Service.
The 38 arrests in Scotland were made after the minibuses were stopped early on Thursday morning in Aberdeen and four addresses were raided in the city's Bucksburn area and in Fraserburgh.
Four of the men held, believed to be involved in organising workers for the fish processing industry, have been taken to Berwick-upon-Tweed for questioning by Norfolk police.
A spokesman for the Grampian force said the remaining arrests were of 34 workers, primarily from the Baltic states, who were being questioned by police and immigration officers.
A Norfolk police spokeswoman said the majority of the workers arrested in Aberdeen had turned out to be in the UK illegally.
Home Office funding
Det Supt Jim Stephen said: "This is by far the biggest operation of its nature which Grampian Police has been involved in.
"An operation of this scale shows the benefits of working jointly across the country."
A further 15 people have been dealt with by the Immigration Service.
The police investigation was part-funded by the Home Office.
The arrests are not connected to the deaths of 20 Chinese cockle-pickers who drowned on 5 February when they were caught on mudflats by a rising tide at Morecambe Bay.