An explosion in the city of Lyon on Friday evening has injured at least seven people.

The small blast occurred around 5:30 pm local time (11:30 am ET) in a central shopping area, near the intersection of Victor Hugo road and Sala road. Its cause has not been fully determined yet.

French President Macron characterized the explosion as an attack, telling an interviewer this evening, “I’m late because there was an attack in Lyon.”

“As far as I can say there are no victims — there are wounded,” he added.

A spokesman for the Lyon prosecutor told CNN that the explosion could have been caused by a parcel bomb packed with nails.

On Twitter, the Auvergne Rhone Alpes regional police said the chief of police and prosecutor were on the scene. It also tweeted photographs of the evacuated scene, and said that a security perimeter has been put in place, asking the public to avoid the area.

Emergency responders are assisting the wounded, a spokesperson for the Police Nationale told CNN, adding that that the priority would be assisting victims, “regardless of if it was a car crash or a terrorist attack.”

“The reasons for the explosions will be searched for later,” they said.