Heathrow Airport’s immigration checkpoint outage resolved after several hours of disruption

International airline passengers arriving at Heathrow Airport near London faced long lines at immigration checkpoints for several hours on Tuesday evening after the British Border Force reported a nationwide computer outage, officials said.

“Border Force is currently experiencing a nationwide issue which is impacting passengers being processed through the border,” Heathrow, the country’s largest airport, said on social media at 9:15 p.m.

Just before 2 a.m. on Wednesday, Heathrow announced that the issue had been resolved, but it was unclear if that was the case for other impacted airports.

Manchester Airport, Gatwick Airport near London, Belfast International Airport in Northern Ireland and several other airports had reported being affected Tuesday evening, though the overall number of affected airports wasn’t clear. 

Officials said that the problem originated with the Border Force’s “eGates,” immigration checkpoints that process arriving passengers through the border. 

Officials at Gatwick and Manchester Airports said Tuesday that there were no flight delays or cancellations related to the outage, but said that they were working with Border Force officials to assist passengers experiencing delays at immigration.

It was unclear when the outage began or what caused it. An inquiry emailed to the U.K.’s Home Office, which administers the Border Force, was not immediately answered Tuesday.

Images on social media showed crammed, stagnant lines in front of a row of gates beneath signs that read “UK Border” at Heathrow Airport.