She said all four of the women, who are in their 20s, have been hospitalized, two of them for shock.
The spokeswoman did not release any further details about the victims or the suspect.
The prosecutor's office could not be reached for comment but told France 3 that one of the women had been hit in the eye with acid and had trouble seeing.
The spokeswoman for the Marseille prosecutor's office said the suspect did not make any extremist threats or declarations during the attack. Since then, authorities have thwarted multiple follow-up attacks by terror organizations, and it has since been revealed that ISIS hoped for much worse carnage while attacking Paris.
Everton defence must improve ahead of Romelu Lukaku reunion, says Ronald Koeman
Three wins and a draw in four games means that the Red Devils are leading the English Premier League on goal difference. We couldn't be happier". "What I did with him was what I do normally with every player - like Jones".
French authorities said they do not believe the attack is terrorism.
The four women were studying overseas, three of them at the college's Paris program.
Regional newspaper La Provence, quoting unidentified police officials, reported that the suspect had a history of mental health problems and noted that she remained at the site of the attack without trying to flee.
The attack took place a train station in Marseille.
United States education Secretary Betsy DeVos visits charter schools in Gary
She will end the tour at Eastern Hancock High School for its football game and pig roast from 6:10 p.m.to 8:30 p.m. Superintendent Cheryl Pruitt and school board president Rosie Washington were also present for her visit.
There was no immediate information on where the USA tourists are from.
No other information on where the US tourists were from was released.
In late August, the southern French port city of Marseille made global headlines when a van rammed into multiple bus stops, killing one person, in an act that authorities determined not to be terrorism.
The female American tourists were sprayed with hydrochloric acid by a 41-year-old at 11am this morning at Saint-Charles station, French media report. He told police he acted in the name of the Islamic State group.
Harry Dean Stanton of Alien and Twin Peaks Fame Dies
Stanton was born in Kentucky to a tobacco farmer father and a hairdresser mother. He starred in both Repo Man and Red Dawn ("Avenge me!") that very same year.