SIMIC

More than two weeks on, the congestion has expanded to nearby Ningbo-Zhoushan as shipowners divert ships to other ports in the country to avoid the trucker shortage and warehouse closures in Shanghai.

There were 222 bulkers waiting off Shanghai this week 15 per cent higher than a month earlier, according to Bloomberg shipping data.

At Ningbo-Zhoushan there were 134 carriers, 0.8 per cent higher than last month, while further north, the combined ports of Rizhao, Dongjiakou and Qingdao saw a 33 per cent increase to 121 vessels.

There were also 197 containerships either loading or waiting to load in Shanghai's combined anchorage with Ningbo, a 17 per cent increase from a month ago.

A shortage of port workers at Shanghai is slowing the delivery of documentation needed for ships to unload cargo, according to ship owners and traders.

Meanwhile, vessels carrying metals like copper and iron ore are left stranded offshore as trucks are unable to send goods from the port to processing mills.