A man was found shot dead inside a UK-registered tradesman's van carrying irregular migrants parked at a rest stop along a northern French motorway, officials said Saturday, prompting a criminal investigation into murder and human trafficking.

The van was discovered early Friday at the Champ l'Épée rest area on the A26 motorway, about 30 kilometres north of Troyes, southeast of Paris and roughly 300 kilometres from the English Channel. Troyes prosecutor Isabelle Verissimo said the body of a 47-year-old man was found around 5 a.m. with "a gunshot wound to his head" on a seat inside the van. Inside the vehicle, police found "around 10 foreign nationals who were irregularly on French territory," Verissimo said, without disclosing their nationalities or that of the deceased man.

A preliminary investigation suggested shots were fired at the rest stop as the van pulled in to park, after which several people fled the scene. A suspect "believed to have been present at the crime scene" was arrested early Friday, according to the prosecutor's office. The law enforcement office in Reims, to the north, is leading the investigation.

The Troyes prosecutor's office said a formal criminal case would be opened Saturday on charges including murder, attempted murder, unlawful possession of a weapon, aiding the irregular entry, movement and residence of a foreigner in France as part of an organised group, and human trafficking as part of an organised group.

The incident underscores the continued use of northern France as a staging area for migrants attempting to reach Britain across the Channel, often transported well inland before being moved toward the coast for a final crossing attempt. Violence linked to smuggling networks operating along this route has recurred periodically in recent years, as competition between rival trafficking groups and the risks of the crossings themselves have drawn sustained scrutiny from French and British authorities.