The French prosecutor's office said on Wednesday that 26 people had been arrested in France and Belgium in connection with the deaths of 39 Vietnamese migrants found in the back of a truck near London last year.
The dead, including two 15-year-old boys, were found on an industrial estate about 20 miles (32 kilometers) east of London last October.
Belgian police arrested 13 people on Tuesday as part of an investigation into the deaths of 39 Vietnamese migrants in a refrigerated truck in Britain.
Prosecutors said those held in raids around Brussels are suspected of running a human smuggling network believed to be behind the tragedy in Britain in October last year.
British media reported last month that Northern Irish truck driver, Maurice Robinson, has pleaded guilty to 39 counts of manslaughter related to the deaths of Vietnamese individuals found in a shipping container in southeast England last year.
The victims included 31 men and boys and eight women between the ages of 15 and 44.
Most of the victims were from north-central Vietnam's Nghe An and Ha Tinh provinces, where poor job prospects, environmental disasters and the promise of financial reward fuel migration.
Robinson, 25, had pleaded guilty at an earlier hearing in November to charges of conspiring to assist unlawful immigration and acquiring cash, which he knew or suspected came from criminal conduct.
Autopsies concluded that the provisional cause of death of the 39 Vietnamese people was a combination of hypoxia, or oxygen deprivation, and hyperthermia, in an enclosed space.
European leaders have been tackling the refugee crisis both within Europe and along its borders; however, the failure to come up with effective policies has left the problem unsolved. The EU relies on Turkey to curb the arrival of refugees into Europe following a 2016 agreement to seal off the Aegean route after more than 1 million people entered the bloc.
The migrants who are being discovered in containers or in the back of trucks barely give a glimpse into the scope of the issue as thousands have lost their lives in the Mediterranean Sea over the years.