France's anti-terrorist office opened an inquiry into the blast and the anti-terrorism prosecutor, Remy Heitz, went to Lyon. The interior minister also was on site, and soldiers secured the area.
France is jittery over a spate of attacks in recent years, some of them deadly, carried out by people ranging from extremist attackers to mentally unstable individuals. Five people were killed Dec. 11 in an attack on the Christmas Market in Strasbourg, in eastern France. The alleged killer, Cherif Chekatt - killed by police - had pledged allegiance to the Islamic State group.
French media quoted the mayor of Lyon's second district, Denis Broliquier, as saying that an image of the man who deposited a sack or suitcase that apparently exploded was captured by surveillance cameras.
Two news TV stations, BFMTV and CNews, showed a blurry image of a man on a bicycle that they said was the suspect.
Broliquier, the district mayor, told BFMTV he arrived minutes after the 5:30 p.m. explosion at the bakery chain Brioche Doree in Lyon's central Presqu'ile area, which lies between the Rhone and Saone rivers that run through France's third-largest city.
"What I saw was a refrigerated cooler in the Brioche Doree, whose windows had been shattered. It was the windows ... that superficially injured the people who were 1, 2 or 3 meters (yards) away," Broliquier said.
"But the fridge itself wasn't that damaged, which means the device had low force," Broliquier said, downplaying the incident. "It's not the apocalypse ... There's no danger. There's no risk."
He said authorities had cordoned off the street but had not evacuated residents. Authorities would not confirm French media reports that the blast was caused by an exploding package.
French President Emmanuel Macron called the explosion an "attack" during a live interview about the European Parliament elections that run through Sunday.
The mayor and Macron sent their sympathies to the injured, some of whom were taken to the hospital and others just went home.
Resident Jean-Pierre, who lives above the bakery and didn't give his last name, told BFMTV the noise from the explosion was "deafening" but it didn't cause the walls to shake. He said a window shattered and there was some debris on the street.
Some victims sustained leg injuries and no wounds were life-threatening, Kamel Amerouche, the regional authority's communications chief, told The Associated Press.
Earlier, French officials said eight people were wounded, but later lowered the figure to seven.
The women's World Cup soccer tournament is scheduled to start in France on June 7. Lyon will host the semifinals, and then the final on July 7.
Interior Minister Christophe Castaner said in a tweet that he has sent instructions for Lyon authorities to strengthen "the security of public sites and sporting, cultural and religious events."
French Prime Minister Edouard Philippe cancelled an appearance at a European elections-related meeting in Paris due to the Lyon explosion.
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