The suspected key figure in a ring of people smugglers has been arrested in Germany over the deaths of 39 Vietnamese migrants in a refrigerated truck in Britain last year, several sources told AFP.
On Tuesday, 26 other suspects were arrested in the greater Paris region and in Belgium in a coordinated police swoop.
The migrants -- 31 men and eight women -- were found dead in the truck in an industrial zone east of London in October 2019.
The driver of the lorry has already admitted manslaughter over the deaths but Tuesday's arrests targeted the ring of smugglers suspected of organising the migrants' journey.
The suspect arrested in Germany's Upper Rhine region is a 29-year-old man nicknamed "The Bald Duke," the sources said.
"He could be the head of the network on the French side," a source close to the investigation told AFP, adding that he had been arrested following a European arrest warrant issued by France.
There were no details of the man's nationality.
Eleven of the 13 suspects arrested simultaneously in Belgium have already been charged by a judge in Bruges with people trafficking, membership of a criminal organisation and fraud, according to Belgian prosecutors.
Most of those arrested in France are also Vietnamese, according to an investigation source.
The probe has discovered that the migrants who died were loaded into the truck in northern France, and that the network continued its operations even after the tragedy, charging 15,000 to 20,000 euros to cross from France to Britain.
Even the coronavirus lockdown did not stop the gang's smuggling activities, the source said.
The tragedy shone a spotlight on the extraordinary dangers migrants are willing to risk to reach Britain, with some paying smugglers up to $40,000 for the perilous journey.
Post-mortem tests found the victims died from lack of oxygen and overheating, and one sent a poignant text message to her family in Vietnam as she lay dying in the truck.
The victims came from poor and remote corners of central Vietnam, a hotspot for people willing to embark on dangerous journeys in the hope of a better life abroad.
Many are smuggled illegally through Russia or China, often left owing huge sums to their traffickers and ending up working on cannabis farms or in nail salons.
The driver of the lorry, Maurice Robinson from Northern Ireland, last month pleaded guilty to manslaughter over the 39 deaths.
Four other men are on trial in London over the tragedy, while another man, Ronan Hughes, is facing extradition from Ireland to Britain on 39 counts of manslaughter and one of conspiracy to commit unlawful immigration.