How do I find information on temporary gas lines?

In five coordinated attacks, the conspirators released sarin gas on several lines of the Tokyo subway, killing twelve people and injuring nearly a thousand others. The attack was directed against trains passing through Kasumigaseki and Nagatacho, home to the Japanese government. This was (and remains, as of 2006) the most serious attack that has occurred in Japan since the end of the Second World War.