From the Foreign Office's travel advice for Spain:
"United Kingdom airlines and the Civil Aviation Authority are concerned about the serious fire risk in hold loaded luggage arising from promotions in Spanish holiday resorts in which cigarette lighters are attached to and/or packed in cartons of some brands of cigarettes. The lighters have a sensitive electronic ignition, which can be activated by movement within a suitcase as it is being transported. Travellers who buy such cartons of cigarettes are advised to remove the lighters and dispose of them prior to their return flight as these lighters should not be carried onboard an aircraft"
http://www.fco.gov.uk/travel/factsheet_fulltext.asp