Federal prosecutors have dismissed all criminal charges against Kseniia Petrova, a 31-year-old Russian scientist who was held in immigration detention for four months after arriving in the United States with frog embryo samples intended for cancer research at Harvard Medical School.
Petrova was arrested in March 2025 after returning from a trip to France, where she visited a laboratory that prepares extremely thin sections of frog embryos. She obtained a package of those samples to support work at her lab in the U.S., and authorities subsequently detained her when she arrived back in Boston.
Her detention lasted roughly four months, during which she faced the prospect of deportation to Russia. The case attracted attention because it involved biological research materials being transported internationally and raised concerns about the treatment and legal exposure of scientists working across borders.
Prosecutors announced the dismissal of the criminal case but public records released with the initial summary do not specify the reasons for the decision. The underlying immigration proceedings and Petrova’s broader legal status were not detailed in the available account.
Petrova had been associated with research at Harvard Medical School, where the frog embryo samples were to be used in cancer-related experiments. The dismissal of criminal charges removes that separate layer of legal jeopardy, though questions about how such samples are transported and handled across international lines remain unresolved in this instance.