Amazon has been quietly shipping thousands of ocean freight containers out of China and to the West Coast, in another sign of its increasing logistics ambitions and an entire supply chain play, according to a report in USA Today.

In the past year Amazon Logistics and its Chinese subsidiary, Beijing Century Joyo Courier Service Co., has shipped 4.7 million cartons of consumer goods, or 5,300 shipping containers, from ports in China to Long Beach and Seattle, according to research from Ocean Audit. For some shippers it also then moves the goods from the port to an Amazon fulfillment center.

While the flow through Amazon Logistics is relatively small compared to the massive volume of trans-ocean freight – 1.81 million twenty-foot equivalents (TEU) of…