TOKYO -- The location had changed, but the scene yesterday was terrifyingly familiar -- gasping passengers staggering away from a train, rescue workers wearing gas masks converging on a rail station after emergency reports of an odd odor.
This time, more than 300 people were hospitalized after the mysterious fumes spread through a commuter train and several stations on the heavily traveled 20-mile route between Tokyo and Yokohama, Japan's second-largest city.
The scene was reminiscent of last month's nerve agent attack in the Tokyo subway that killed 12 people and injured more than 5,000. But there were differences, too: No one died in yesterday's incident, and authorities were better prepared to respond -- even though they remained unsure today who had carried out the attack.
Police said they could not say what the fumes were, though they ruled out sarin, the nerve agent reportedly used in the subway attack last month. The Tokyo Fire Department said that one person who had been hospitalized was diagnosed as having been exposed to phosgene, a poison used in World War I and sometimes used in the manufacturing of plastics.
Authorities arrested the No. 2 figure in Aum Shinri Kyo, or "Supreme Truth," the sect suspected of responsibility in the Tokyo attack. Police identified the man as Kiyohide Hayakawa, 45, and described him as the sect's deputy leader, second only to founder Shoko Asahara, who has eluded a huge manhunt.
Mr. Hayakawa was charged in connection with a break-in at a garage where a car was found containing parts used in making guns. The charges did not directly link Mr. Hayakawa either to the Tokyo subway attack or to the attack in Yokohama.
In Yokohama, train passengers saw a liquid, then noticed an odor like sulfur or paint thinner. Victims suffered coughing, dizziness and nausea.
Authorities said the gassing resembled a March incident on the same train line that sent 11 passengers to hospitals. The incident received little publicity at the time.
This time, policemen were stationed at train stations, where they watched the vast waves of commuters coming into Tokyo for work. The first notification of a new disaster reached the Yokohama station at 12:50 p.m., shortly before the affected train arrived.
Police and hospital crews were dispatched within minutes. At 1:50 p.m., a military chemical weapons unit followed. By 2 p.m., when the last affected passengers stumbled off the train, the rescue effort was under way and Yokohama Station, which usually serves 1.5 million passengers a day, was closed.
Police and firefighters searched for clues, and 1,000 police remained throughout the day. Television stations pre-empted soap operas for live reports, and newspapers published extra editions.