The audacious raid in the eastern city took place on Thursday afteronoon, with police quickly arresting the suspected perpetrators and recovering the loot estimated at €12 million (US$13.8 million), officials said.

Five employees of Laboratoires Pourquery were “slightly injured in the explosion” and three were taken to hospital for checks, the regional prefecture told AFP.

Twenty-eight employees were present when the robbers struck.

The suspects, believed to be seasoned criminals, were detained shortly after in the neighbouring town of Venissieux, a source close to the case told AFP.

A woman, an accomplice who took part in the robbery, was also arrested, a police source told AFP.

“Six people who used explosives in an attack on a precious metals company in Lyon were caught red-handed,” interior minister Laurent Nunez said on X, praising officers for their “firmness, speed and control.”

Assault rifles, handguns and explosives were also seized.

The robbery took place as French police on Thursday arrested five more people, including a prime suspect, over this month’s brazen Louvre museum robbery.

Dozens of detectives have been hunting for four thieves who used a truck with a moving lift and cutting gear to break into a first-floor gallery at the museum on Oct 19, fleeing with jewellery worth an estimated US$102 million.

In another high-profile break-in, thieves last month broke into the French capital’s Natural History Museum, making off with gold samples worth more than US$1 million.

A 24-year-old Chinese woman was arrested earlier this month in Barcelona over the break-in and theft, prosecutors said.

The string of robberies has stoked concern about inadequate security at museums and other places holding high-value items.