( CNN ) -- Southwest Airlines is working with federal and local officials to determine who is responsible for vandalizing its planes with strange markings , a statement from the airline said Tuesday . The unauthorized markings surfaced in February , spokesperson Whitney Eichinger said in the statement . Eichinger would not comment on the number of planes vandalized , where the incidents were reported or give specific details about what the markings were . CNN affiliate KNXV in Phoenix reported that multiple sources , who asked not to be identified because they were not authorized to speak on behalf of the company , have said `` the markings appear to be Arabic words . '' But those same sources said they believe the markings are the work of `` an employee or group of employees joking around , '' KNXV reported . Southwest had planned to handle the situation as `` an internal vandalism issue , '' a memo from Mike Van de Ven stated , but a company employee called in a tip to ABC15 , after information about the investigation was posted in a memo on the company 's internal blog . `` We are asking your help to stop this and to report those responsible , '' the memo from Mike Van de Ven read . `` If you are aware of anyone involved in marking or tagging our aircraft , please notify our Leader , `` the memo states . It also said `` the issue is taken very seriously , '' and that the company plans `` to work in cooperation with both local and federal law enforcement agencies until the issue is resolved . ''
Employees received an internal complaint about markings on planes . Southwest is working with local , federal officials to find vandals . They told local media , ' the markings appear to be Arabic . ''