07:39 – 07:59 Five members of Aum Shinrikyo board separate trains on different lines of the Tokyo underground system. They each drop between two and three packets of sarin onto the carriage floor and puncture them before leaving the train. They escape with the help of five other members of the group, who are waiting near designated stations in getaway cars. Passengers begin to experience the first symptoms of exposure to sarin.

08:00 At Kodenmacho station, a passenger kicks one sarin packet from the train onto the platform where it leaks and forms a puddle. This will lead to the deaths of four people.

Station staff clearing the sarin package collapsed and died from exposure to the fumes.

08:10 On the same train, a passenger pulls the emergency cord and the train stops at the next station, Tsukiji. Several passengers collapse onto the platform when the doors open and the train is immediately taken out of service.

08:17 The first reports of toxic fumes are made.

08:30 A train is evacuated and searched at Ikebukuro station. The sarin packets are not discovered and the train resumes its journey a few minutes later. Over the next hour, it is cleaned and the packets are removed, but it is not taken out of service until 09:27.

08:40 The first casualty arrives at St. Luke’s International Hospital.

08:50 Emergency medical stations are set up outside underground stations to deal with the increasing numbers of casualties.

11:00 Police confirm the incident is a sarin gas attack.

* Images from Zero Hour program