Five suspects in the burning of an Air Nuigini Dash 8 plane in Mendi remain at large and police are still searching for them.
The plane was destroyed during unrest in the Southern Highlands capital in June when the local courthouse and provincial governor's residence were also burned down.
The National newspaper reported Mendi station police commander Leo Walaget saying the suspects' identities were known to police.
He said other suspects had been arrested and charged.
The police were still trying to restore law and order with the help of a platoon of Defence Force soldiers and a supportive community, the commander said.