BERLIN — An assailant poured a liquid over a woman on a tram in eastern Germany on Sunday and set her alight, police said. The woman was taken to a hospital with life-threatening injuries, while the attacker fled.

Police said no other people were hurt in the incident in the eastern city of Gera, German news agency dpa reported. Passengers stopped the tram by pressing an emergency button, and the assailant took the opportunity to flee.

The tram driver immediately began to extinguish the flames, and the 46-year-old woman was taken to a hospital by helicopter.

Police were searching for the assailant. It wasn’t immediately clear what prompted the attack, or what exactly the liquid was.