The suspected attacker was seen by a police patrol car carrying a knife a short distance from where the attack took place.
The scene was cordoned off by police as the investigation continues.
A source close to the police said witnesses heard the attacker shout “Allah Akbar”, or “God is great”.
Police spokesman said this information was being verified.
Another source close to police also said the victim was beheaded in the attack, but this has not been confirmed.
French newspaper Le Parisien reported that the victim had been “horribly mutilated”.
The report also added that the attacker was a parent of a student, but this has yet to be confirmed by police.
The French Minister of the Interior, Gérald Darmanin, who had visited Morocco, is returning to France as a matter of urgency.
French police tweeted urging members of the public to avoid the area.
They wrote: “Avoid the boulevard de la commune de Paris sector and the corner of Boulevard Salengro in Eragny sur Oise. ”
In recent years, France has suffered a number of violent attacks carried out by Islamist militants.
Last month, a man who migrated to France from Pakistan attacked and injured two people with a meat cleaver outside the former offices of satirical magazine Charlie Hebdo.
It was at the same location that Islamist activists shot and killed publication employees in 2015.
It was in retaliation for the magazine’s publication of cartoons of the Prophet Muhammad.
It’s a story of rupture. More soon…