"Around 6.30am (04.30 GMT), three armed criminals went into the Primark store for what we think was initially an attempt at armed robbery," an anonymous police source said of the incident at Villeneuve-la-Garenne.
An employee told her boyfriend via SMS at about 7.00am that the holdup was taking place, saying that she and some colleagues had been taken hostage by two armed men.
Later about 18 Primark employees left the shop and went to a cafeteria in the Qwartz shopping centre where the incident took place.
All the other shops had closed and police had sealed off the area.
They were taken out of the mall at about 10.30am but police did not know if the robbers were still there.
They later said that they believed they had fled the scene.
They were three in number and had been filmed by CCTV entering the mall.
One of them was reported to have been identified as a Primark employee.