The Governor of the Northern Marianas, Benigno Fitial, has been asked to investigate fuel prices set by oil suppliers on Saipan.
Representative Stanley T. Torres says Mobil and Shell raised their prices before the price of crude oil hit over 126 US dollars a barrel.
The two companies are selling regular petrol at $4.49 a gallon and premium at $4.59.
The Marianas Variety newspaper reports that Representative Torres has asked why the two increased their prices when they were still selling supplies purchased before the price of crude oil increased.
Mr Torres claims that the latest increases are not for fuel purchased at a higher rate.
The oil firms have previously told the newspaper their prices are dictated by market prices in Singapore where they get their fuel.