Brazil's oil regulator ANP dialed back the reduced biofuels mandatory blend in Rio Grande do Sul state to four cities amid the recent flooding in the region.
Low blending areas now apply only to the cities of Canoas, Esteio, Rio Grande and Santa Maria. The measure will still last for 30 days, starting on 4 May.
ANP lowered the anhydrous ethanol blend on gasoline to 21pc from the current 27pc in the entire state earlier this week, while pushing the mandatory biodiesel mix for 10ppm (S10) diesel down to 2pc, from the usual 14pc.
The agency also temporarily suspended the blending mandate for diesel with 500ppm of sulfur (S500).
ANP said it decreased the exemption's coverage as it identified "that the supply situation in the rest of the state had stabilized."
Rainfall in Rio Grande do Sul blocked railways and highways where biofuels are transported to retail hubs.
Floods in the state have left at least 116 dead and 143 missing, according to the local government.