Paris police say a person on the city's subway has been seriously injured after being burned with an "unknown liquid" in what French media have described as an acid attack.
The unidentified victim was attacked in the metro's line one, near the station of Bastille, during rush hour Friday morning.
The person, reported to be a man in his 20s, is being treated for major burns to the face and hands after being evacuated by the emergency services.
Police say an inquiry is underway and that the perpetrator is at large.
On Wednesday, a man and a woman were burned by what was believed to be sulfuric acid on the metro but police said there was no link. In that case the acid had been poured onto a flip down seat and the floor of the train car.
In Sept 2017, two American college students were injured in a hydrochloric acid attack by a woman at a train station Marseille, southern France.
The Associated Press contributed to this report.