Swiss police say five people remain in critical condition — including the suspect — after a man attacked train passengers with a knife and a burning liquid.

St. Gallen canton (state) police spokesman Hans-Peter Kruesi told The Associated Press on Sunday that authorities have not been able to interrogate the 27-year-old suspect about his motive due to his condition.

Kruesi said that so far police have found no indications he had ties to extremist groups.

The attack occurred Saturday afternoon as the train neared the station in Salez, close to the Liechtenstein border.

Police say the suspect, identified as a Swiss man from a neighboring canton who was not known to police, is seen on video attacking passengers with the burning liquid and a knife, injuring seven in all.