A French Gendarme blocks the access road to the Saint-Quentin-Fallavier industrial area, near Lyon, France. [Photo/Agencies]

The site belonged to Air Products, a US industrial gases and chemicals company, according to a spokeswoman for Air Liquide, a French company in the same sector. It was immediately ringfenced by police and emergency services.

The chairman and CEO of Air Products is Seifi Ghasemi, who in 2011 testimony to a US Senate committee described himself as Iranian-born. Mainly Shi'ite Iran is a sworn enemy of Sunni-dominated Islamic State.

No group claimed responsibility for the attack and the motive was unknown.

French Interior Minister Bernard Cazeneuve was at the site in the town of Saint-Quentin-Fallavier, around 30 km (20 miles) southeast of the city of Lyon.

French media said the government had ordered security to be stepped up around sensitive sites in the surrounding Rhone-Alpes region.