Ukrainian film director Oleh Sentsov is not listed among the inmates of the Labytnangi penal colony (Yamalo-Nenets Autonomous District of the Tyumen Region), the prison administration said in its response to a query of human rights activist Yana Honcharova, which was published by Sentsov's sister Natalia Kaplan.

"There are reports that Oleh Sentsov is not in IK-8 (penal colony No. 8) in Labytnangi. This is what Yana Honcharova learnt from a letter from the colony. They refused to give any information to me in the prison call center. Nobody answers the phone at the colony chief's office," Kaplan wrote on her Facebook page on Tuesday.

She said that the letter was sent on Sunday, February 25, through the Federal Penitentiary Service's electronic system, the answer came on Tuesday, February 27.

"We begin our search," Sentsov's sister stressed.

The letter from the administration of the colony says: "The administration of IK-8 Labytnangi informs you that the letter can not be delivered, because its recipient is not kept in this institution."

As reported, the North Caucasus Military Court in Rostov-on-Don ruled in August 2015 to sentence Sentsov, who had been detained in Crimea in 2014, to 20 years in a high-security penitentiary on charges of setting up a terrorist group in Crimea.

Sentsov is reportedly serving his sentence in high-security correctional facility number eight (also dubbed Polar Bear) is located just outside the Yamalo-Nenets town of Labytnangi. Its inmates are male convicts sentenced for serious and very serious crimes.

The Ukrainian authorities have repeatedly called the Sentsov case politically motivated. In May 2016, he filled out documents for a transfer to Ukraine to serve his term there. The Russian Supreme Court declined to review his appeal. The Ukrainian Justice Ministry said in fall 2016 that Russia had refused to extradite the Ukrainian.