LONDON – Britain’s Home Office is investigating how a passenger was allowed to board a flight from Spain to Britain without a passport.

Officials said Wednesday the passenger was questioned by Border Force agents at Liverpool John Lennon Airport after he landed there on a flight from the Canary Islands.

The statement said the passenger was allowed to enter Britain after agents “carried out identity checks and established that he was a British national who previously held a valid passport.”

It said it was the airline’s responsibility to make sure each passenger has proper documents.

The Daily Mail newspaper said the passenger used a photocopy of a bus pass to board the Ryanair flight after his passport was stolen.

Ryanair said in a statement it has a duty to repatriate nationals on their return flight to their home country.

“If a passport is lost or stolen, we ask that an alternative, or a copy of, photo ID is provided in order to verify the passport details the customer provided at the time of check-in,” it said.