The roof of a building at Mahon airport on the Spanish island of Menorca has collapsed, injuring at least two people, BBC reported. The collapse occurred at about 1200 local time during installation works to fix wall grids, Spanish newspaper El Mundo said. The cause of the collapse is not yet known but Spanish authorities believe it to be an accident. El Mundo had said on its website that 20 workers, including both Menorcans and Portuguese, were trapped under the rubble. However the regional interior ministry said no-one was trapped. There have been heavy rains on the Mediterranean island over the past few days, but it is not known if that played a part in the accident.