On Feb. 29, the chairman of the House Committee on Homeland Security, Rep. Mark Green, R-Tenn., sent a strongly worded letter to an obscure Chinese equipment manufacturer: Shanghai Zhenhua Heavy Industries Co. (known as “ZPMC”). ZPMC is the world’s top producer of ship-to-shore gantry cranes used at container terminals the world over — nearly 80% of the cranes at U.S. ports are ZPMC cranes, and the company has a higher share in Europe.

The subject of Green’s letter wasn’t a trade dispute of the kind that has erupted between China and the U.S. in the past five years, but something rather more serious: accusations ZPMC secretly installed communications devices in cranes bound for the U.S. that would enable spying and even remote control (or sabotage) of the cranes.

Green wrote that “cellular modems” were found in the cranes which were completely extraneous to the functioning of the cranes and were not covered in the purchase agreements between U.S. port authorities and ZPMC. Green noted that ZPMC’s proximity to elements of the Chinese security and intelligence apparatus — the company’s base is adjacent to the Jiangnan Shipyard at Shanghai where China builds warships — could allow the Chinese military to exert undue influence on the manufacture of the cranes. The letter pointed out that because Liu Chengyun is both ZPMC’s chairman and president and also serves as the chairman of the company’s internal Communist Party committee, there is nothing in ZPMC’s corporate governance that would mitigate the Chinese Communist Party’s influence at the company.

The letter was not just a one-off missive responding to a headline in the 24-hour news cycle. It was the result of a congressional investigation by the Committee on Homeland Security and the Select Committee on the Strategic Competition between the United States and the Chinese Communist Party (CCP) that began in June 2023. But suspicions about the CCP leveraging maritime infrastructure to spy on the United States have been brewing for years, as the letter makes clear. It was back in 2021 when FBI agents discovered “intelligence gathering equipment” aboard a ship delivering gantry cranes to the Port of Baltimore.