TOKYO -- Japanese police on Wednesday 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 one 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. The train was travelling from Tokyo to Osaka.

Investigators searched Hayashizaki's apartment in Tokyo, looking for clues to his actions. Television video showed them carrying out cardboard boxes filled with confiscated items. Police said they haven't yet determined the motive.

Japanese media quoted his neighbours as saying he had repeatedly complained that his meagre pension was barely enough to live on.

The transport ministry said the incident was the first fire on a bullet train in its 50-year history.

Many Japanese mourned the second victim, Yoshiko Kuwahara, who had written on her Facebook page that she was travelling to a Shinto shrine at Ise to pray and give thanks for her "peaceful and safe" life in the first half of the year. As an osteopath, she said her dream was to "heal the pain in the heart and body of other people."

As the nation tried to recover from the shocking incident, transport officials met with bullet train operators to seek ways to tighten security without affecting the efficiency of the trains.

Transport Minister Akihiro Ohta told the meeting that it would be important to step up luggage controls, also as part of anti-terrorism and fire-prevention efforts.

"Naturally, safety comes first, but convenience is also important," he said.

Some officials said Japan needs stricter security on its bullet trains ahead of next year's Group of Seven summit in Japan and the 2020 Tokyo Olympics. But experts say it would be impossible to conduct airport-level luggage checks for the high-speed line, which operates trains every three minutes during rush hours.

The 16-car bullet trains, called shinkansen in Japanese, travel the 553 kilometres between Tokyo and Osaka in 2 hours and 33 minutes.