Maui fire investigators say an arsonist is to blame for two fires at Maui High School Friday morning.  Incendiary devices were found at each site. The first fire was reported just after 5:30 a.m. Firefighters say someone tried to ignite a 55-gallon drum containing used motor oil near the entrance to Building L, but the barrel did not burn.  Then, just after 7 a.m. firefighters were called back after fire broke out in a portable classroom.  The fire was extinguished before firefighters arrived.  Damage is estimated at $5,000.