ST. PETERSBURG, Russia — Russian investigators have dropped charges against all but one of the 30 crew of a Greenpeace ship, who were accused of hooliganism following a protest outside a Russian oil rig in the Arctic, the group said Wednesday.

Cristian d’Alessandro of Italy failed to get his criminal case closed due to the lack of an interpreter and will have to visit the St. Petersburg branch of Russia’s Investigative Committee again today, said Violetta Ryabko, a Greenpeace spokesman.

The criminal charges against the crew were closed under an amnesty that was passed by the parliament earlier this month, seen by many as an attempt by the Kremlin to dampen the criticism of Russia’s human rights record before the Winter Olympics in Sochi in February.

Ryabko said foreign members of the crew had already applied to the Russian authorities for exit visas to leave Russia and expect to get them in the next few days.

The 30 crew members aboard a Greenpeace ship were detained in September and held in custody for two months before they were released on bail in November. They were originally charged with piracy, but that was then downgraded to hooliganism.

“That was an extremely odd Christmas morning,” Frank Hewetson of Britain was quoted by Greenpeace as saying Wednesday.