An “imposter” attempting to enter the United States through B.C. last month using a family member's passport and vaccine card was stopped thanks to facial recognition technology, U.S. officials said on Monday.

A statement from U.S. Customs and Border Protection (CBP) says biometric facial comparison technology detected a facial mismatch while a passenger was being processed at the Pacific Highway port of entry bus terminal, located between Surrey, B.C., and Blaine, Wash.

The woman later admitted to using her sister's U.S. passport and COVID-19 vaccination card because she had not been vaccinated, according to the agency. CBP did not say what the woman's nationality is.

"The addition of facial biometric technology and the vigilance of our CBP officers helped intercept someone suspected of fraudulently using another individual's passport and COVID-19 vaccination card to cross international borders," Brian J. Humphrey, director of field operations at CBP's Seattle field office said in a statement.

U.S. Customs and Border Protection says the biometric facial comparison process, known as Simplified Arrival, occurs "only at a time and place where travellers are already required by law to verify their identity by presenting a travel document."

"When a traveller arrives at one of the pedestrian lanes or undergoes I-94 processing, he or she will pause for a photo at the primary inspection point. A CBP officer will review and query the travel document, which will retrieve the traveller's passport or visa photo from government holdings and compare it to the new photo."

CBP describes the process as taking only a few seconds and more than 98 per cent accurate, with new photo comparisons of U.S. citizens deleted within 12 hours. It says photo comparisons of most foreign nationals are stored in a "secure U.S. Department of Homeland Security system."

More than 113 million travellers have participated in the process at air, land and seaports of entry, according to CBP, with biometric facial comparison preventing more than 1,100 people using genuine travel documents issued to other people in order to illegally enter the country.

"U.S. travellers and foreign nationals who are not required to provide biometrics and wish to opt out of the new biometric process may notify a CBP officer as they approach the primary inspection point," the agency says.

"These travellers will be required to present a valid travel document for inspection by a CBP officer and will be processed consistent with long established processes for admission into the United States."

All non-immigrant or non-U.S. citizens travelling to the U.S. by air are required to be fully vaccinated.

Airline passengers to the U.S. aged two and older, regardless of vaccination status or citizenship, must also provide proof of a negative COVID-19 test taken within one day of travel. Travellers may, alternatively, provide documentation from a licensed health-care provider of having recovered from COVID-19 within 90 days.

Fully vaccinated foreign nationals may enter the U.S. for tourism or other non-essential purposes at land ports of entry and ferry terminals, and do not require proof of a negative test.

Travel to the U.S. from Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa and Zimbabwe is currently restricted due to concerns over the new Omicron variant.