AMSTERDAM, Netherlands (AP) _ Dutch police said Wednesday they have arrested five more men and are seeking another, allegedly part of a ring that tried to smuggle 58 Chinese immigrants into Britain inside a sealed truck, where they suffocated to death.

Dutch police claimed ``remarkable progress'' in their investigation, saying they had traced the rented warehouse where the immigrants were put into the large truck for the ill-fated ferry trip across the English Channel.

The gruesome discovery of the 58 corpses at the English port of Dover 10 days ago threw light on the huge illicit trafficking of people, mostly from Asia to western Europe, which United Nations officials described as the world's fastest growing international crime. Two migrants survived the journey.

The five new arrests bring the number of suspects in Dutch custody to seven. Another suspect ``is still on the run,'' the prosecutor's office said in a statement. Another man was detained and released after several days, it said.

``The Dutch police have managed to get a pretty clear picture of the organization and of the individuals that have been organizing the transport,'' the office's Unit of Illegal Human Trafficking said.

All the suspects were men from the Rotterdam area, it said.

It said the ``front man'' for the operation was Arie van der Spek, who registered the trucking company that carried the Chinese to their deaths and whose arrest was one of two previously announced.

In addition, British police were holding the driver of the truck, and two ethnic Chinese allegedly linked to the smuggling ring.

A warehouse in Waalhaven, a part of the Rotterdam harbor, was identified as the assembly point for the immigrants. They were brought there in small vans, then loaded onto a truck bought by Van der Spek's company and driven to the Belgian port of Zeebrugge, from where they were ferried to Dover.