(London) The British government on Wednesday ruled out the hypothesis of a cyberattack to explain the failure Tuesday evening of the gantries automatically controlling passports at airports, causing long delays for passengers.

The gantries, which scan biometric passports and use facial recognition, were out of service for four hours on Tuesday evening, starting at 8 p.m. local time.

“At no time has border security been compromised and there is no indication of malicious cyber activity,” the Home Office said in a statement.

This incident occurred when, earlier on Tuesday, the government indicated that it could not rule out state involvement in a cyberattack against a Ministry of Defense service provider, managing the payroll system, with contact details personnel of 272,000 soldiers. Some MEPs pointed to China, which firmly denied it.

The failure of the gantries affected British airports such as London-Heathrow or London-Luton, Edinburgh or Manchester, where border police had to manually check passports.

In Luton, passengers were forced to queue in their hundreds for more than an hour to go through passport controls.

Disruptions had already been reported two weeks ago due to problems affecting the gantries at several British airports.

Rail was affected by a strike on Wednesday over wage demands, while last week Heathrow Airport saw a four-day strike by Border Police officers against the end of the assignment of certain officers to passport control.