WASHINGTON (Sputnik) - Russian national Maria Butina, sentenced to 18 months in US prison, was transferred from a detention center in Alexandria, Virginia, to another location, the official US notification system has said.

"Maria Butina has been transferred from the Alexandria Sheriff's Office as of May 10, 2019", the notification read on Friday. The location where Butina has been transferred to is unknown.

According to the federal inmate locator service on the agency's website, Butina will be eligible for release on 5 November 2019. She will have served nearly 16 months in US prison by that time, after having been arrested on 15 July 2018.

Butina's lawyer Robert Driscoll confirmed to Sputnik that she had been transferred from a prison in the US city of Alexandria, Virginia. "She is gone from Alexandria Detention Centre. Do not know where yet", Driscoll said on Friday.

The timetable for the early release presumably reflects the fact that Butina, like all prisoners in the United States, could get time reduced from her sentence in exchange for good behavior in custody.

READ MORE: Stranger Tries to File Court Motion in Butina Case on Her Behalf — Lawyer

On 26 April, a US federal court sentenced Butina to 18 months in prison after she pleaded guilty to a single count of conspiring to act as an unregistered foreign agent. Butina, who signed her plea deal after being held for long periods in isolation in prison, had requested a sentence of time served.

The Russian Foreign Ministry has called Butina's sentence a disgrace to the US judicial system and has accused the US court of carrying out a clear political order.

In November, the Russian Embassy in the United States said US authorities kept Butina in a single cell under solitary confinement for 67 days, exceeding the limit recommended by the Nelson Mandela Rules for the treatment of prisoners.

Russian President Vladimir Putin has said Butina’s indictment was unjustified because she was not charged with any mission on behalf of the Russian government.

Robert Driscoll told reporters last month that Butina hopes to qualify for an early release based on good conduct time in prison.

READ MORE: Butina May be Transferred to Prison in Alabama or West Virginia Soon — Priest