Police searched the Greenpeace International ship early Thursday after the arrest of four Greenpeace members who scaled a tower near an incinerator plant in Tokyo to protest Japan's waste-incineration policies.
The 555-ton Dutch-registered Rainbow Warrior is berthed at Tokyo port as part of an Asian tour campaigning for a toxic-free Asia.
The four, identified by a Greenpeace spokesman as being Belgian, British, Chinese and Dutch nationals, were arrested Tuesday on suspicion of trespassing. Several other activists at the site voluntarily went to a police station for questioning.
The four had climbed the tower of the world's tallest incinerator in Toshima Ward's Kami-Ikebukuro district, and near the top, dropped a large banner proclaiming Tokyo the world's "dioxin capital."
In a statement, the environmentalist group said the act was to protest "Japan's reckless waste-incineration policy," which results in Japan having the highest total emissions of dioxins and furans in the world. Dioxins and furans are toxic chemicals often produced by incineration.