MOSCOW, Oct 9 (Reuters) - Russian investigators said on Wednesday they found drugs aboard a Greenpeace ship that was used in a protest against offshore Arctic drilling and would press new charges against some of the 30 people being held for alleged piracy.
In addition to drugs, the Investigative Committee said searches of the Arctic Sunrise, which was boarded by Russian coast guards after the Sept. 18 protest at the Prirazlomnaya oil rig, had revealed equipment with potential military uses.
It also said investigators were trying to establish which of those being held were responsible for what it called attempts to ram coast guard boats, endangering the lives of their crew.
"In view of the data obtained while investigating the criminal case, charges ... are expected to be adjusted," the committee said. It said that "a number of detainees will be presented with charges of committing other grave crimes."
Russia arrested the 28 activists and two freelance journalists who were aboard the Dutch-registered Greenpeace vessel during the protest and has charged all of them with piracy, which is punishable by up to 15 years in prison.
The Investigative Committee said morphine and poppy straw, a ingredient for heroin and opiates, were found on the ship.
Greenpeace lawyer Alexander Mukhortov said the vessel's American captain legally kept morphine in his safe for medical purposes, and expressed doubt about the other claim by investigators.
"The Investigative Committee 'found' narcotics. We are waiting for it to find an atomic bomb and a striped elephant. This is possible in Russia these days and can hardly surprise anybody," Greenpeace Russia said on its Twitter account.
The environmentalist group says the piracy charges are absurd and unfounded and that the conditions of detention for the detainees, who come for 18 countries, have in some cases violated their civil rights.
Kumi Naidoo, the head of Greenpeace, offered in a letter to Russian President Vladimir Putin on Wednesday to move to Russia and stand as security for the release on bail of the detainees.
The Netherlands launched legal proceedings against Russia on Friday, saying it had unlawfully detained the activists and others on the Dutch-registered icebreaker Arctic Sunrise.
Reporting by Gabriela Baczynska; and Maria Tsvetkova in Moscow, Thomas Escritt in Amsterdam, editing by Mark Heinrich