Tongan police say investigations into last month's riots are continuing.
According to a government survey, a total of 143 businesses were damaged and some were totally burnt down.
The police commissioner, Sinilau Kolokihakaufisi, says they have arrested a number of people.
"A total of 668 persons have been arrested and out of that 99 are still in custody. Well, on different charges, ranging from drunkeness to theft, unlawful damage, arson."
The majority of suspects are aged between 21 and 30, but 63 are under age.
The police commissioner says he cannot explain why most suspects are so young.