Prosecutors say a Swiss man who attacked passengers aboard a train with a knife and a burning liquid, killing one and wounding five, didn't know any of his victims, according to the investigation so far.

St. Gallen canton prosecutors' spokesman Roman Dobler said Tuesday that investigators haven't found any indication that the 27-year-old attacker was linked to any kind of extremism.

He said that "at the moment there is no indication that the suspect had a political or religious motivation... and also no indication that the suspect knew any of the victims."

Seven people including the suspect were initially wounded in the Saturday afternoon attack. On Sunday, the assailant, identified only as Simon S., and a 34-year-old woman he had attacked died of their injuries. Three victims remain hospitalized.