The three men -- one of whom was thought to be an employee of the shop -- burst into the Primark store in Villeneuve-la-Garenne early today, said a police source who wished to remain anonymous.
An employee first alerted her boyfriend to the hold-up at around 7:00 am (0500 GMT) when she sent him a text message saying they had been taken hostage by two armed men, another source said.
The mall was promptly evacuated but according to police, 18 employees had remained inside -- some were told to stay put by the gunmen and others had managed to hide on their own.
They "were evacuated around 10:30 am, one of them was unwell but no-one was injured," police said.
But while security forces initially thought the gunmen were still inside the mall, they realised after searching the premises that the men had escaped.
Memories of attacks in January by Islamic extremists who gunned down 17 people in and near Paris -- including several who were held hostage in a Jewish supermarket -- are still fresh in many minds in France.
France, and the Paris area in particular, is still on high alert and some 7,000 soldiers are deployed around the country to help police in countering any further attack.
But so far police have indicated Monday's attack was a common armed robbery.
"The tallest... Had a gun, I think it was a pump-action shotgun. The other man was smaller.
"I was at the store's stockroom door, they passed in front of me... They went to the offices," he said.
"I heard 'this is a hold-up, you must go' several times... I turned around and took the lift.
"They were definitely looking for money, it's a store that is doing very well."
A London-based spokesman for Primark, a low-cost clothing store that has been a huge success in Britain, confirmed there had been an "incident" at its store, which is located just north of Paris.
