Amazon has begun shipping products from Chinese merchant partners to its U.S. warehouses via ocean freighters, the Wall Street Journal reports. This is something it used to outsource exclusively, and another piece of the overall shipping and logistics picture that it’s now controlling directly, at least in part.

Amazon doesn’t own ships, or employ crews, but it now acts as a logistics provider and organizer for carriers that do own those vessels. That means it will book cargo space on ocean-faring ships, and that will transport goods from those ships to warehouses and vice versa. Other freight forwarders include FedEx and UPS, for example.

The ecommerce giant has so far acted as a freight forwarder for at least 150 containers of goods imported from China, over a period dating back to October, the WSJ says.

Previously, Amazon revealed plans to handle more air transport for goods sold via its website through a leasing agreement for Boeing cargo jets dubbed Amazon Prime Air. The company also handles more of the last mile delivery process on its own via contracted courier services in cities where it offers same-day and Prime Now two-hour shipping.

Owning more of its logistics business is a key way for Amazon to help control costs, especially as its business continues to scale. The retailer now owns a dominating percentage of online and overall consumer goods sales, especially in the U.S., which means that it makes sense for it to take on responsibility for ever bigger chunks of that logistics supply chain.

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