Before the massacre, French detectives questioned one of the jihadis behind Friday's terror attacks as he crossed the Belgian border but let him go after he showed them his ID card.
Officers pulled over Salah Abdelsam on Saturday morning on the A2 motorway between Paris and Brussels. He was travelling with two other people, just hours after he abandoned a car containing three Kalashnikov AK-47 assault rifles on the outskirts of the French capital.

Detectives soon realised their error when they discovered  that Abdeslam had rented VW Polo abandoned near the scene of the massacre inside the Bataclan theatre.
However, by the time they alerted Belgian authorities, the jihadi had abandoned the car in the jihadi stronghold of Molenbeek, Brussels and disappeared.
An international manhunt has since been launched to apprehend him.

French security officials have admitted that Abdeslam was one of three men inside the car which had been stopped on the border on Saturday morning. Officers in Paris had already identified Salah Abdeslam as a person of interest but that information had not been transmitted to those responsible for conducting the border checks.
Abdeslam's brother Ibrahim, 31, blew himself up in a solo attack outside cafe Comptoir Voltaire. He had rented a black Seat. That car was found with with AK-47s and ammunition in the Paris suburb of Montreuil. A third brother, named Mohamad has been arrested in the Belgian capital.
It is believed the team of eight may all have gathered in a Belgian suburb called the 'Jihad capital of Europe' to collect their AK-47s and suicide vests. French and Belgian police are investigating links between the international cell and the Molenbeek area of Brussels known as a 'den of terrorists'.

Iraqi intelligence warned US-led coalition countries of an imminent assault the day before the Paris attacks, it has emerged.
At least one of the terrorists was a Parisian who had been on a terror watch list for five years, but was not being monitored closely enough to be stopped before he took part in the murderous attack.
Greek authorities believe that two of the gunmen sneaked into Europe posing as a refugee from Syria – heightening fears that not enough security checks are being carried out on migrants.