Story highlights The driver stabbed himself twice after the incident, but is expected to survive

An investigation is just beginning, a spokesman for France's Interior Ministry says

At least 9 are injured after a van plows into shoppers at a Christmas market

It's unclear if it's related to a similar incident Sunday, when a vehicle rammed into pedestrians

A van plowed into shoppers at an outdoor Christmas market Monday in Nantes, France, injuring at least nine people in addition to the driver, police said.

Four had serious wounds, plus the driver, police said.

The driver stabbed himself twice after the incident, but is expected to survive, said Pierre-Henry Brandet, a spokesman for France's Interior Ministry.

French Interior Minister Bernard Cazeneuve will head to Nantes Monday evening to meet with the families of the victims and rescue officials, Brandet told CNN affiliate BFM-TV.

The investigation is just beginning, he said, but so far the Nantes prosecutor has said the incident appears to be an isolated case and not a terrorist attack.

Authorities are investigating a notebook found with the attacker, Brandet said.

It was not immediately clear whether the incident was related to one Sunday in Dijon, France, in which witnesses said a man shouting "God is great" in Arabic rammed his vehicle into pedestrians.

At least 12 people were injured by that vehicle, said police in Dijon, a city in eastern France. A man has been arrested in connection with the case, they said.

BFM-TV reported that eyewitnesses heard the driver shout the phrase "Allahu Akbar" -- Arabic for "God is great."

On Saturday, a man stabbed three police officers in central France while allegedly calling out the same phrase. French counterterrorism authorities are investigating that attack.

And France's Prime Minister said earlier Monday that his country has never faced as serious a terrorism threat as it does right now.

Police haven't revealed any possible motives in the vehicle incidents.