Sanctioned Russian billionaire Arkady Rotenberg sold his shares of oil and gas services construction firm Stroygazmontazh to a mysterious new company.

Rotenberg sold the company at the beginning of November for about RUB 75 billion (USD 1.2 billion), according to Russian media, though Stroygazmontazh’s corporate records were not updated until Thursday. The new owner, a company called Stroyinvestholding, was registered in July. Its ownership is not publicly disclosed.

Stroyinvestholding’s founder and director general is Olga Safonova, who founded at least five other companies across Russia, corporate records show. The companies, all now dissolved, specialized in wholesale trade of machinery, lumber, and other construction materials, according to corporate records.

Rotenberg, who has called Stroygazmontazh his “brain child,” concluded the sale with a subsidiary of Gazprom, though Stroyinvestholding, the current owner, has no apparent connection to the Russian gas giant. Rotenberg has not commented on the sale, Russian business daily RBC reported. Stroygazmontazh posted revenue of RUB 304 billion in 2018, according to Interfax.

Attempts to sell Stroygazmontazh were first announced in March, as the company sought to mitigate the sanctions risk of Gazprom, according to Russian media reports at the time. Stroygazmontazh is a key contractor for two Gazprom pipelines -- the Power of Siberia pipeline slated to send gas to China by the end of this year, and the Gryazovets-Slavyanskaya pipeline that will feed into Nord Stream 2.

Stroygazmontazh was sanctioned by the U.S. Treasury Department in April 2014 for being owned by Rotenberg, a billionaire associate of President Vladmir Putin who “amassed enormous amounts of wealth” during Putin’s presidency, according to the Treasury. Stroygazmontazh was sanctioned by the European Union in July 2018 for its involvement in building the Kerch Bridge linking Russia and Crimea. Gazprom is on a separate U.S. sanctions list targeting Russian firms in the energy sector, though its assets aren’t blocked.