Russia is considering new charges against the Greenpeace members it is holding over an Arctic oil rig protest.
The 29 Greenpeace activists and a freelance Russian journalist have been charged with piracy. The charge carries a sentence up to 15 years.
A spokesman for Russia's Investigative Committee said that "dual-use equipment" and drugs were also found on the Greenpeace ship, Arctic Sunrise and it was expecting to charge several with more "grave crimes" once they have established their role in the protest.
He said that investigators are trying to identify the people whose inflated boats were standing in the way of Russian coast guards, thus "threatening life and safety of an official," a grave offence in Russia.
The head of Greenpeace International has written to Russian president Vladimir Putin requesting a meeting in Moscow - and offering himself as human bail for the detainees.
Kumi Naidoo of the Amsterdam-based organisation delivered the letter to the Russian embassy in The Hague saying he would guarantee the activists' good conduct but said that piracy charges do not make sense and should be dropped.