Imports of livestock from the U.K. will grind to a halt at the Port of Rotterdam next month should Britain crash out of the European Union, as a vital inspection point at the harbor isn’t ready.

“We face a couple of hiccups and livestock is one of them,” Mark Dijk, the port’s manager of external affairs, said in an interview last week. “Although it is positive that we got a bit of an extension.” In the absence of a deal or a further delay, Brexit is now scheduled for April 12, rather than the original deadline of March 29.

Rotterdam’s port is a crucial gateway for imports from Britain to the Netherlands and the rest of the EU, handling about 40 million tons of shipments between the two nations each year. Port operators on both sides of the British Channel are rushing to get ready for Brexit after decades of tariff-free trade between the U.K. and the bloc.

The Dutch Food and Consumer Safety Authority, which oversees inspections of livestock, has hired about 100 veterinarians in advance of Brexit, but the building where checks will occur is still under construction.

“For us, there are still many uncertainties,” Liesbeth Kooijman, head of imports for the authority, said in a presentation last week. “We are preparing for a worst-case scenario.”

Almost three years after the U.K. voted to leave the EU, the terms of the departure remain in flux. Britain’s Parliament has seized control of the Brexit agenda from Prime Minister Theresa May after she twice failed to win backing for the divorce agreement she hammered out with the EU. While she’s still fighting to get her deal passed in time to avoid a cliff-edge departure, Parliament is set to weigh support for alternative proposals.

If the deal is passed, then a transition agreement would keep the current customs rules in place until the end of 2020. After that, the U.K. would become a so-called third country from the EU’s standpoint, meaning customs clearance would be required for all U.K. trade with the bloc. About 35,000 of the more than 80,000 Dutch companies that do business with the U.K. have never dealt with the paperwork involved in trading outside the EU, the Dutch customs authority has said.

Rotterdam, which handles more than 465 million tons of shipments a year, has about 3,000 trucks loaded with cargo destined for Britain pass back and forth through the port each day. Additional parking areas with space for more than 700 trucks have been created for those that don’t have their paperwork in order.