New York, New York - A Harvard researcher who fled Russia fearing political persecution has been released from US custody after being targeted for deportation by the Trump administration.

Kseniia Petrova was detained by Immigration and Customs Enforcement (ICE) agents in February at a Boston airport after she failed to declare biological samples in her luggage upon returning from a trip to Paris.

Officials told Petrova that her visa was revoked and that she would be sent back to Russia before transporting her to an ICE detention center.

Petrova, a scientist at Harvard Medical School, was later charged with smuggling, criminal offenses that carry a maximum 20-year prison sentence and a $250,000 fine.

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She was freed on pre-trial release in the smuggling case Thursday by Judge Judith Dein in Boston, with another hearing on her detention scheduled for next Wednesday.

"I'm relieved Kseniia Petrova has been released, but she never should have been detained in the first place," said Andrea Campbell, Massachusetts attorney general.

"This administration is taking taxpayer dollars and resources that could be spent on improving lives to instead instill fear."

Christina Reiss, chief judge for the US District Court in Vermont, ordered Petrova's release in late May from ICE custody, though she had remained in detention for the smuggling case.

Petrova has claimed she fears returning to Russia because of the risk of arrest after participating in political protests, notably against the war in Ukraine.