Japanese police have searched the apartment of the man who set himself on fire on a high-speed bullet train, killing himself and another passenger, as officials sought clues to his motive.

Investigators identified the man as 71-year-old Haruo Hayashizaki. He poured an oil-like liquid over himself and set fire to it at the end of a train car on Tuesday, filling the coach with smoke and killing himself. A 52-year-old female passenger died from suffocation after suffering throat burns.

Police said they haven't determined the motive.

Transport officials met with bullet train operators on Wednesday to discuss how they can tighten security without affecting the efficiency of the trains.