GRAYS (AP) -- Authorities found 39 people dead in a truck in an industrial park in England on Wednesday and arrested the driver on suspicion of murder in one of Britain's worst human-smuggling tragedies.

Police were reconstructing the final journey of the victims as they tried to piece together where they were from and how they came to be in England.

"To put 39 people into a locked metal container shows a contempt for human life that is evil," said Jackie Doyle-Price, a member of Parliament who represents the area where the truck was found. "The best thing we can do in memory of those victims is to find the perpetrators and bring them to justice." 

The truck and the trailer with the people inside apparently took separate circuitous journeys before ending up on the grounds of the Waterglade Industrial Park in Grays, 25 miles (40 kilometers) east of London on the River Thames.

British police said they believe the container went from the port of Zeebrugge in Belgium to Purfleet, England, where it arrived early Wednesday. Police believe the tractor traveled from Northern Ireland to Dublin, where it took a ferry to Holyhead in Wales before picking up the trailer at the dockside in England.

The truck's driver -- a 25-year-old man from Northern Ireland -- was arrested on suspicion of murder. He has not been charged and his name has not been released.

The truck was registered in Bulgaria to a company owned by an Irish citizen, Bulgaria's Foreign Ministry said. It's point of origin was unclear. The Belgian federal prosecutor's office said it has opened an investigation.

"We have no idea at the moment how long the lorry (truck) spent in Belgium," said spokesman Eric Van Duyse. "It could be hours or days. We just don't know."

As darkness approached Wednesday, a police motorcycle escort slowly led the Scania semitrailer out of the industrial park, taking it to a place where the bodies could be recovered. The driver of the trailer wore a full forensic suit and gloves as he guided the massive vehicle in the impromptu cortege past journalists.

Britain remains an attractive destination for immigrants, even as the UK is negotiating its divorce from the European Union. In Parliament, Prime Minister Boris Johnson put aside the Brexit crisis and vowed that human traffickers would be prosecuted to the full extent of the law.

"All such traders in human beings should be hunted down and brought to justice," he said.

Ambulance workers discovered the bodies after being called at 1:40 a.m. It was unclear who called the ambulance service.

No cause of death has been made public. Police said one victim appeared to be a teenager but gave no further details.

The number of victims was shocking, although it has become sadly common in recent years for small numbers of migrants to occasionally be found dead in sealed vehicles after having been abandoned by traffickers.

The tragedy recalls the death of 58 migrants in 2000 in a truck in Dover, England, and the deaths in 2015 of 71 migrants from Syria, Iraq and Afghanistan who were found suffocated in the back of a refrigerated truck that was abandoned on an Austrian highway close to the Hungarian border.

Groups of migrants have repeatedly landed on English shores using small boats for the risky Channel crossing, and migrants are sometimes found in the trunks of cars that disembark from the massive ferries that link France and England, but Wednesday's macabre find in an industrial park was a reminder that trafficking gangs are still profiting from the human trade. Police also were investigating a separate incident in which nine people were found traveling in the back of a truck in southeast England.

The National Crime Agency said its specialists were working to "urgently identify and take action against any organized crime groups who have played a role in causing these deaths." It said in May that the number of people being smuggled into Britain via cargo trucks was on the rise. (AP)