“All means have been activated to identify and detain the person who committed this act,” Paris prosecutor Remy Heitz told media in Lyon, the third-biggest French city.
The blast occurred just two days ahead of hotly contested European Parliament elections and with France on watch for any repeat of recent deadly terrorist attacks which have rocked the country.
Heitz has taken charge of the investigation into “attempted murder in relation with a terrorist enterprise and association with terrorist criminals.”
French Justice Minister Nicole Belloubet said late Friday however that it was too soon to say whether the blast could be termed a “terrorist act”.
President Emmanuel Macron initially called the Friday evening explosion an “attack” but later took a more cautious tone with a tweet that condemned “the violence that has struck” the city's residents.
Police issued an appeal for witnesses on Twitter as they sought the suspect, a man believed to be in his early 30s on a mountain bicycle caught on security cameras in the area immediately before the explosion. An image of the man, wearing light-coloured shorts and a longsleeved dark top, was posted. He was described as “dangerous”.
Police have released this CCTV image of the man they want to speak to
The number of wounded stood at 13 people, with 11 taken to hospitals. None of the injuries was life-threatening. The casualties comprised eight women, a 10-year-old girl, and four men.
No one has claimed the attack, Heitz noted.
He said investigators had recovered small screws, ball bearings and batteries along with a printed circuit and a remote-controlled trigger device, and pieces of white plastic that might have been part of the explosive device.
It was placed in front of a bakery near a busy corner of two popular streets at around 5:30pm Friday, on a balmy spring evening. The blast occurred on a narrow strip of land between the Saone and Rhone rivers in the historic centre of the southeast city. The area was evacuated and cordoned off by police.
District mayor Denis Broliquier said “the charge was too small to kill,” and an administrative source told AFP it was a “relatively weak explosive charge” that was triggered at a distance.
“There was an explosion and I thought it was a car crash,” said Eva, a 17-year-old student who was about 15 metres from the site of the blast. “There were bits of electric wire near me, and batteries and bits of cardboard and plastic. The windows were blown out,” he said.
'A huge 'boom'
The attack upended last-minute campaigning ahead of the European Parliament vote on Sunday with Prime Minister Edouard Philippe cancelling his appearance at his centrist party's final rally Friday night.
A terrorism probe was opened by the Paris prosecutor's office, which has jurisdiction over all terror cases in the country. Interior Minister Christophe Castener was on his way to Lyon.
“I was working, serving customers, and all of a sudden there was a huge 'boom',” said Omar Ghezza, a baker who works nearby. “We thought it had something to do with renovation work. But in fact it was an abandoned package.”
France has been on high alert following a wave of deadly jihadist terror attacks since 2015 which have killed more than 250 people.
“It's an area in the very centre of Lyon, a major street,” the city's deputy mayor in charge of security, Jean-Yves Secheresse, told BFM television.
“These areas are highly secured, the police are continually present,” as were patrols by soldiers deployed in a long-running anti-terror operation, he said.
Lyon is the third-biggest city in France. The population of the city plus its extensive suburbs is 2.3 million.
The most recent package bomb in France dates back to December 2007, when an explosion in front of a law office in Paris killed one person and injured another. Police never found who carried out that attack.
By AFP's Pierre Pratabuy