SAINT-QUENTIN-FALLAVIER (France) - One suspect, named as Yassin Sahli, had been arrested, and police were holding at least one other suspected accomplice in the attack near Lyon yesterday, in which a decapitated body daubed with Arabic writing was found at a US industrial gas company.
The assailant, who rammed a car into the premises, triggering an explosion, survived the blast and was arrested.
A source close to the investigation said the victim was the boss of the suspect, a delivery man. The two had gone to the company to make a delivery but the assailant killed and beheaded his 50- year-old manager before entering the secured site in the vehicle.
The head of the victim, who ran a delivery service, was found pinned to the gates at the American-owned Air Products factory in Saint-Quentin-Fallavier. It was surrounded by two Islamist flags.
His body was found inside the factory, the site of what French President Francois Hollande called a terrorist attack.
Sahli, 35, is suspected of driving one of the delivery service's vehicles into the factory grounds. Though access to the facility is restricted because it contains dangerous substances, the delivery company had clearance to enter.
Interior Minister Bernard Cazeneuve said Sahli did not have a criminal record but had been under surveillance from 2006 to 2008 on suspicion of having become radicalised by Islamists.
"A person was killed and decapitated and the anti-terrorist section of the Paris prosecutor has been immediately deployed," Mr Cazeneuve said at the scene of the attack in an industrial zone, 30km south-east of Lyon.
French media said Sahli was a professional driver who lived in the Lyon suburbs. There was no official confirmation of that but Europe 1 radio interviewed a woman they identified as his wife.
"In the morning he left for work and didn't come home between noon and 2pm, I was waiting for him," she told Europe 1 radio, saying she and her family of three children lived normal lives as Muslims. "My heart is about to give out."
It was not known whether the victim, so far the only known fatality in the incident that also injured two people, was decapitated before or after the car smashed into the building.
"We all remember what has happened in our country, and not just in our country. So there is plenty of emotion. But emotion cannot be the only response - that must be action, prevention and dissuasion," Mr Hollande said.
Saint-Quentin-Fallavier, with its good air, rail and road links, is one of Europe's major logistics hubs, venue to some 1.5 million sq m of depots, with through-traffic of 5,000 trucks a day.
The attack underlined again the difficulty for authorities across Europe and elsewhere of protecting so-called "soft" targets against strikes by assailants operating by themselves or in small undercover cells.
France, which has deployed aircraft to the international coalition fighting Islamic State in Iraq and Syria (ISIS) insurgents in Iraq, has long been named on Islamist sites as a primary target for attacks.
REUTERS, AGENCE FRANCE-PRESSE