A spokeswoman for the prosecution told AFP that the attack, which caused seven people to be a booby-trapped parcel.
The Le Parisien website quoted a police source as saying that a man on a bicycle was seen placing the parcel.
Another source called for "the need to be cautious while not sure whether the incident is a terrorist act or settling accounts."
Police reportedly found nails and bolts at the site of the blast.
Accounts on Twitter circulated pictures of the street that witnessed the blast.