SBU officials claim that Ruslan Zabily, head of the Prison on Lontskoho Museum in the western city, planned to transfer information to third parties, information that they claim is classified and a state secret.
Speaking to RFE/RL on September 9, SBU spokeswoman Maryna Ostapenko declined to specify what kind of information was involved and who the alleged third parties were.
Zabily, whose museum is dedicated to the victims of Soviet and Nazi rule, denies any wrongdoing. At a press conference in Kyiv, he said that he was detained on September 8 at the train station in Kyiv upon arriving from Lviv and interrogated for more than 14 hours, without official sanction.
Zabily, 35, said his laptop and two hard discs were confiscated. According to the historian, he was questioned about his contacts with foreign academics and was advised to get a job as a school teacher.
Zabily said that the confiscated data concerns the activities of the Ukrainian Insurgent Army, a partisan army which fought against the Soviets and Nazis in World War II, and the Soviet-era dissident movement -- documents which have long been declassified.
The Prison on Lontskoho museum was established in 2009 under the auspices of the SBU. Zabily is a historian by training. The museum shows visitors conditions in which detainees lived and places where mass executions took place.
The museum is housed in a 19th-century building that was built to house the Austro-Hungarian gendarmerie. It has served as a Polish, Soviet, and Nazi prison.
Volodymyr Viatrovcyh, the former chief archivist of the SBU, believes that the new authorities are trying to pressure historians who are researching the Ukrainian liberation movement.
Since the beginning of this year, a number of Ukrainian civic activists, journalists, and bloggers have voiced concern over increased interest from the SBU. Several have been called in for "conversations" and been issued warnings.
Earlier this week, Yevhen Bystrytskyy, the director of the International Renaissance Foundation in Kyiv, said that the secret service was checking the activities of its partners in the Kyiv region.
In comments to RFE/RL on September 7, Bystrytskyy described the move as pressure on Ukraine's civil society and the first such case in more than 10 years. The foundation is financed by American financier and philanthropist George Soros.
Later the SBU announced that it had no issue with the Renaissance Foundation and explained its interest toward local NGOs as ensuring that they do not breach the election law.