Arson investigator FO2 Rodolfo Centeno said they found bottles of crude oil inside the PAL office along Alunan Avenue.
"Talagang may intention na sunugin (There was really an intention to burn it)," Centeno said.
Probers said the fire started in a cabinet where office files were kept.
The blaze struck at about 1:20 a.m. and was placed under control in 10 minutes. Ramil Bajo