Russian authorities have charged all 30 people aboard a Greenpeace ship with piracy after two activists tried to scale an oil platform in a protest of Arctic drilling last month, the Russian Investigative Committee said Thursday.

The charging began Wednesday and finished Thursday. If convicted, the 28 activists and two freelance journalists could be sentenced to up to 15 years in prison.

None of the 30, who hail from at least 18 countries, pleaded guilty, the committee said.