Updated

Germany's top administrative court has ordered plans to deepen the Elbe River be revised because of potential risks to a rare aquatic plant.

The ruling sent shares in logistics company HHLA, which operates container terminals at the Port of Hamburg, tumbling more than 11 percent Thursday.

The Federal Administrative Court in Leipzig said current plans don't sufficiently take into account the impact that increased salt content from the North Sea could have on the Schierlings water fennel that's found only in the Elbe. It also found fault with measures to preserve nature reserves further upriver.

Shipping companies want the Elbe to be deepened so large container ships can reach Hamburg at high tide.

The port, Germany's biggest, is located 100 kilometers (62 miles) away from the North Sea.