French President Francois Hollande said a suspect was arrested and identified in what he called a "terrorist" attack and explosion at a U.S. gas factory that killed at least one person in the country's southeast.
The attack occurred Friday at a factory owned by Air Products, a U.S.-based industrial gases technolgoy company, on the outskirts of the southeastern city of Lyon.
A human head was found pinned to the gates of the factory, reportedly accompanied by a banner or flag with Arabic writing.
"It is a terror attack, no doubt about it," Hollande told a news conference in Brussels. He learned about the attack with German Chancellor Angela Merkel as both leaders attended a European Union summit in Brussels.
While details are still sketchy, the president said at least two other people were injured in the attack, which took place around 10 a.m. local time (0800 GMT).
Hollande said the other factory workers have been evacuated and security has been heightened around the factory.
France opened a terrorism investigation shortly after the attack Friday.
Witnesses at the factory in the small town of Saint-Quentin-Fallavier, about 30 kilometers (18 miles) southeast of Lyon, said at least one attacker drove a car onto the company grounds and set off at least one explosion.
Police said it was unclear whether the attacker was acting alone or had accomplices.
Hollande called on French citizens to stand in solidarity as the details of the attack are sorted out. He is expected to meet with his defense council later Friday.
French Interior Minister Bernard Cazeneuve called the incident a "heinous crime" and said the threat has been "neutralized." He said the person who was arrested is being questioned and had been known to police since 2006.
Prime Minister David Cameron spoke to Hollande Friday to convey his sympathies over the gas factory attack.
"The Prime Minister has just spoken to President Hollande to express his sympathies for what looks like an appalling incident there," the source said.
Attacks six months ago
It also came nearly six months after Islamist attacks in and around Paris, at the headquarters of the satirical magazine Charlie Hebdo and at a kosher supermarket, bookending a three-day seige of violence that left 20 people dead, including three attackers.
France has a high proportion of people that have gone to fight alongside Islamists in Iraq and Syria and has been on alert for possible attacks on its soil since the Charlie Hebdo attacks.
Earlier this week, the country passed a controversial new spying law granting sweeping powers to snoop on citizens.
Lisa Bryant contributed to this report from Paris. Some material for this report came from Reuters, AP and AFP.