Airports around the United States are experiencing delays in processing international travelers, due to a nationwide outage affecting the computer systems used by Customs and Border Protection. JFK, LAX, SFO, PHL, O’Hare, Midway, Sea-Tac and other airports are confirming delays.

“US Customs and Border Protection is experiencing a temporary outage with its processing systems at various air ports of entry and is taking immediate action to address the technology disruption,” a CBP official said in a statement to The Verge.

“CBP officers continue to process international travelers using alternative procedures until systems are back online. Travelers at some ports of entry are experiencing longer than usual wait times and CBP officers are working to process travelers as quickly as possible while maintaining the highest levels of security.”

At 6:34 PM ET, the CBP tweeted that “systems are coming back online,” and that there “is no indication the disruption was malicious in nature at this time.”

I was finally able to check in for a flight before actually getting to the airport .... & now US Customs systems are down NATION WIDE! Line is crazy & getting crazier. pic.twitter.com/RctYJbEFrF — Ali Ahmad (@AliAhmad03) August 16, 2019

Travelers at airports around the country posted videos of massive, slow-moving lines that sprung up as a result of the outage, including New York City’s JFK airport and Los Angeles’ LAX.

Here’s a better perspective of the customs line at JFK. People are growing frustrated. Nothing like landing after a 10 hour flight to this. pic.twitter.com/WrEUsoJhbH — Sarah Baird (@Baird_S) August 16, 2019

Dulles International Airport near Washington, D.C. stopped being able to process international passengers since 3:18 PM ET, a spokesman told Bloomberg late this afternoon, adding that “the line is beginning to build.” But there were some reports that the system was already spinning back up, including one from Seattle-Tacoma International Airport at 5:34 PM ET and one from from LAX at 6:03 PM ET.

All Customs systems down at PHL. Landed 45 minutes ago. Still in line at Global Entry. #phl #uscustoms #BorderPatrol pic.twitter.com/HUJhdapdx2 — Joe Martella (@jmartella2) August 16, 2019

O’Hare International Airport in Chicago tweeted that both O’Hare and Midway airports were affected by the outage, and Seattle-Tacoma Int’l, San Francisco Int’l and Philadelphia Int’l all tweeted about the Customs and Border Protection’s advisory.

Following the CBP’s announcement that the outage was over, airports including SFO and O’Hare warned that there may still be longer than usual wait times due to “residual delays”.

It’s not clear yet what caused the outage, but we’ll update if we hear.