Five British nationals of Pakistani origin were being questioned on Tuesday after they were arrested while behaving suspiciously at Islamabad Airport, according to government officials. They were arrested along with five Pakistan nationals after they were seen swapping boarding cards with them. All ten suspects were being questioned as officials sought to discover why they had exchanged their boarding passes. A spokeswoman for the British Foreign Office last night denied any British nationals had been arrested and said that all suspects were Pakistanis. Her statement was contradicted however by Pakistani officials who insisted ten were arrested, of which five were British nationals. According to a Pakistan immigration official, the five British nationals were booked onto a flight to Manchester, believed to be operated by a local airline, Air Blue, while the Pakistani nationals were due to board a flight to Dubai, United Arab Emirates. They had already completed immigration and security checks, including having their photographs taken, and were in the departure lounge when they were arrested. A Foreign office spokeswoman said there was no indication that the incident was terrorism-related, while other sources suggested the motivation for swapping boarding cards was more likely to be illegal immigration into Britain by the Pakistani nationals. "We're investigating their motives. We will not be commenting further," said a Pakistan interior ministry official.