U.S. investigators are examining whether Chinese shipping container manufacturers deliberately reduced production in 2019, shortly before the COVID-19 pandemic began, according to sources familiar with the matter.

The investigation focuses on a small number of Chinese firms that collectively control the majority of global unrefrigerated shipping container manufacturing. These companies dominate the industry that produces the standardized metal boxes used to transport goods across oceans.

Investigators are looking into allegations that these firms slowed container production during 2019, the year before the pandemic erupted and created massive disruptions to global supply chains. The timing of any production cuts relative to the pandemic's emergence appears to be a key focus of the probe.

Shipping containers became critically scarce during the pandemic as global trade patterns shifted dramatically, with increased demand for goods shipments coinciding with supply chain disruptions. Container shortages contributed to shipping delays and increased costs that affected international commerce.

The investigation's scope and potential implications remain unclear, as does whether investigators suspect the timing of any production cuts was coincidental or deliberate. No charges or formal accusations have been announced in connection with the probe.