At least four hooded individuals went to the site of the Schneider Electric company in Moirans (Isère), on the night of Saturday to Sunday, for a robbery.
Around 3 a.m., they handcuffed the security guard, who was not injured, said Grenoble prosecutor Eric Vaillant.
"During this armed robbery, boxes of silver powder were stolen, with damage at this stage estimated at around one million euros," he said.
The Grenoble prosecutor's office entrusted the investigation to the research brigade of Saint-Marcellin (Isère), while no robber has yet been arrested.
A convenience store in Le Havre robbed by men with hidden faces
Hooded and armed, he robs a Creil bar-tobacco then returns to apologize