France has been placed on high alert for the next three days after a person was found decapitated in what officials called a “terrorist” incident at a gas factory in southeastern France.

French President Francois Hollande, speaking in Brussels, said the incident began shortly before 10am local time on Friday after a car crashed the gate and ran into gas canisters, causing an explosion. At least two others were injured in the attack.

A security official said a severed head was found posted on the gate at the entrance to the factory, located in Saint Quentin Fallevier, about 30km southeast of Lyon. According to legal sources, the man decapitated was the boss of the suspect now in police custody.

Two flags, one white and one black, both with Arabic inscriptions, were found nearby, a security official told the AP news agency.

“The attack was of a terrorist nature since a body was discovered, decapitated and with inscriptions. As I speak, there is one fatality and two injured,” said

President Hollande, speaking in Brussels.
A French prosecutor said four people were in custody and that police were still searching buildings for evidence.