From a nondescript seventh-floor office at 135 Bonham Strand near Hong Kong’s financial district, at least four companies are operating with a shadowy mission: facilitating the illicit trade of Western technology to Russia.

Shell companies at that address have acquired millions of restricted chips and sensors for military technology companies in Russia, many of which have been placed under sanctions by the U.S. government, according to an examination by The New York Times.

The companies have names like Olax Finance and Rikkon Holding. Their office, with a faded 704 number on the door, appears unoccupied. No one answered during a visit last month. An ad for air-conditioning hung in the crack of the door.

Yet the companies are a crucial link in a chain connecting U.S. research laboratories to Chinese factories, Russian arms makers and the battlefields of Ukraine — and a sign that the U.S. government and tech giants cannot control where their technology goes.

Since Russia invaded Ukraine in 2022, nearly $4 billion of restricted chips have poured into Russia from more than 6,000 companies, including those at Hong Kong’s 135 Bonham Strand, according to a Times analysis of Russian customs data, corporate records, domain registrations and sanctions data. The analysis examined nearly 800,000 shipments of restricted electronic goods into Russia since mid-2021.