Facial recognition gates at Manchester Airport were temporarily taken out of use after a couple walked through the scanners after swapping passports.
It is believed the pair passed through the gates in Terminal One on the morning of 8 February.
The UK Border Agency said they were stopped by the immigration officer supervising the gates afterwards.
It said use of the gates was suspended while an investigation was carried out but they later reopened.
Brodie Clark, head of Border Force at the agency, said there was no breach of security or immigration control.
'Safe and secure'
He said: "E-Gates are used in conjunction with manual checking by border officials and in this case both individuals were stopped by the immigration officer responsible for supervising the gates.
"The E-gates were temporarily suspended whilst an investigation was carried out.
"The investigation concluded that no other sites were affected, and the border was not compromised as a result of the incident.
"The gates have now reopened and we will continue to monitor their performance to ensure they operate safely and securely. To date more than three million people have used the E-Gates system."
The facial recognition gates scan passengers' faces and compare them to the photographs digitally stored on their passports.
They can be used by adult biometric passport holders from the UK and Europe.
They were first tested at Manchester Airport in 2008.