Fire brigade vehicles and ambulances are seen near the site of a suspected bomb attack in central Lyon, France, May 24, 2019. Photo: Reuters / Emmanuel Foudrot.

French police have arrested a 24-year-old Algerian computer student suspected of planting a bomb in Lyon last week that wounded 13 people, authorities said on Monday.

Three other people were also arrested in connection with the case, which is being treated as a terrorism investigation.

A man was spotted by security cameras leaving the explosive device, with screws and metal balls packed into a paper bag, in a pedestrian shopping street in the central French city on Friday a minute before it exploded.

Sources close to the investigation said the Algerian student who is the main suspect did not have police records, while the other three detainees included his mother and younger brother who is a high school student.

Police found the man thanks to security camera footage, Lyon Mayor Gerard Collomb told BFM TV station.

Footage showed a partially masked man wheeling a bike to the scene before leaving a bag outside a bakery. Police then tracked him to a suburb of Lyon.

DNA traces were found on the remains of the parcel, according to sources close to the investigation.

Another source said judicial police tailed the man on Monday and arrested him as he alighted from a bus in downtown Lyon.

Police searched the suspect’s home but decided not to arrest him there, the source said, for fear there could still be some triacetone triperoxide or TATP, the powerful but unstable homemade explosive used in the attack.