A nationwide outage of the Canada Border Services Agency's primary inspection kiosks and NEXUS caused serious delays for passengers arriving at Vancouver International Airport Sunday.

According to the airport, international passengers and U.S. passport holders were being affected the most. By 3:30 p.m. PT, the airport said on Twitter the kiosks were back up and running.

Kiosks are back up and running at YVR. Truly appreciative of everybody’s patience today as we processed arriving passengers, and thankful to the employees who worked hard to help throughout the issue. Sincere apologies to those who were inconvenienced. <a href="https://t.co/hLvT1HgyJT">https://t.co/hLvT1HgyJT</a> —@yvrairport

Jenny Duncan, a spokesperson for Vancouver International Airport, said YVR was notified of the outage around 7 a.m. Pacific Time and international flight arrivals began to get busier around 11 a.m.

Duncan said an hours-long outage of the CBSA systems is "very rare" and CBSA staff were working to resolve what she believed to be a technical issue.

Airport staff tweeted at around 1:30 p.m. that they were working to help arriving guests fill out customs forms manually, as well as keep people hydrated.

A number of other airports across Canada have taken to Twitter to warn travellers about similar issues, including Ottawa, Calgary, and Toronto's Pearson International Airport.

We are still waiting for <a href="https://twitter.com/CanBorder?ref_src=twsrc%5Etfw">@CanBorder</a>’s Primary Inspection Kiosk and Nexus systems to come online. With a number of Intl aircraft arriving this pm, there will be delays but are doing our best to help guests. We apologize for the inconvenience. —@FlyYYC

A representative from the Canada Border Services Agency did not immediately respond to a request for more information.

In an emailed statement, Christopher Richards of YVR media relations said the airport is working with their partners at CBSA to process passengers.