Vienna - An EasyJet flight from Vienna to London was halted just before take-off on Saturday because a passenger believed the man sitting next to her might be an Islamic extremist, authorities said."The woman believed that she saw messages related to ISIS [Islamic State] on the man's mobile phone," Austrian interior ministry spokesperson Karl-Heinz Grundboeck told AFP.The woman alerted cabin crew, security staff were called, the take-off was cancelled and all passengers and all their luggage were taken off the plane for checks."Nothing was found however, and the aircraft has since taken off, but without either the man or the woman. They are now being questioned," Grundboeck said.The man is an Iraqi citizen, he added. It was unclear what the woman's nationality is. The incident comes amid heightened security in Europe following Tuesday's bombings in Brussels, which were claimed by ISIS.