The four young women were in Marseille traveling while studying overseas.
She said a 41 -year-old female suspect has been arrested.
More on this as it develops.
Deputy Metropolitan Police Commissioner Craig Mackey said investigators believe the spike reflects an emerging trend among criminal gangs. Two of the women were treated for shock. The spokeswoman told the AP that the suspect did not make extremist threats.
Four American women were attacked with acid outside a French train station today.
In total, fourteen firefighters arrived on the scene at Marseille's main railway station, which is one of the busiest in France.
She did not release any further details about the suspects or the victims, including where in the United States the tourists were from.
In August, a man driving a van crashed into two bus stops in the Vieux-Port area, a popular tourist spot.
The young tourists were reportedly about to board a train for Paris at the time of the incident.
The attacker did not shout any slogans to suggest the attack was linked to extreme Islamism, according to reports. She also showed pictures of her burns and stated that he had been attacked with acid and wanted others also injured as she is, according to the newspaper.