Brazil's president ordered her top diplomat Wednesday to probe Russia over the fate of a Brazilian activist arrested after protesting Arctic oil drilling.
President Dilma Rousseff said the Foreign Ministry was determined to provide "any assistance" to the Brazilian woman, Ana Paula Maciel.
"I asked Foreign Minister Luiz Alberto Figueiredo to make high-level contact with the Russian government to find a solution for Ana Paula," Rousseff wrote on Twitter.
Maciel was one of 30 activists from 18 countries arrested by Russia in late September and charged with piracy after authorities said they had found "narcotic substances" on the Dutch-flagged Arctic Sunrise, used in the protest.
Investigators added that some of the equipment on the vessel was of "dual purpose" and "could have been used not just for ecological purposes."
Greenpeace has denied the allegation as a "smear."
The Brazilian detainee's mother sent a letter Wednesday to Rousseff, asking for her help.
"I humbly ask that you use your political clout, as head of state, so that President Vladimir Putin can be sensitized and intercede for Ana, who has spent so many years working peacefully for a better world," wrote Rosangela Maciel.
Russia is preparing new charges of "other grave crimes" against some members of the detained crew, with no signs of clemency despite international protests.
Putin has said that the activists "of course are not pirates," but his spokesman Dmitry Peskov later said the Kremlin strongman had expressed his personal opinion.