Police investigating Friday evening's explosion which injured 13 people in the south-eastern French city of Lyon are still searching for the principal suspect. The inquiry has yet to establish the identity and motivation of the presumed attacker.
Traces of DNA found on the backpack at the centre of the explosion have not been identified. This suggests that the suspect is not already on the national register of genetic imprints.
The chemical used to cause the explosion is believed to have been triperoxide of triacetone, already involved in the jihadist attacks in Paris in November 2015 and Brussels in March 2016. The explosive can be produced at home and is known to be extremely unstable.
The French justice minister, Nicole Belloubet, has said it is too soon to be sure if Friday's attack can properly be called a terrorist act.
No individual or group has claimed responsibility for the blast.
The police continue to sift through the evidence provided by dozens of eye-witnesses.