Trucks will be able to access a blocked entrance at Santos, Brazil’s largest port, at night while firefighters finish extinguishing a blaze at a nearby fuel-storage facility, city and port authorities said.   The more flexible rules will provide some relief for grain exports that have slowed since Monday, when authorities restricted truck access to terminals on one side of the port while flames are extinguished. The port authority later said the entrance would be blocked again on Thursday morning as significant cleanup would be required even when the fire was out.   The firefighters’ office in Sao Paulo state said via Twitter that one of six fuel tanks at the facility operated by Ultracargo, a unit of Brazilian chemical and fuel-distribution company Grupo Ultra, was still on fire.   Highway police are escorting truck convoys past the blocked entrances, and 750 passed through in a convey on Tuesday. Even more should get through on Wednesday, the Santos manager of port affairs Jose Eduardo Lopes said. Brazil, the world’s No. 2 soybean producer, has nearly finished harvesting a record crop. Santos moves a third of the country’s exports of the commodity. Archer Daniels Midland Co has a terminal on the Santos side of the port but a press spokeswoman declined to comment on whether operations had been affected.   That side is also home to sugar terminals operated by Copersucar and Cosan SA’s Rumo Logistica. Officials at both companies said sugar was still arriving at the terminals by train, minimizing the impact on exports. Brazil is still a few months away from peak sugar exporting season. A  press agent for Louis Dreyfus Commodities said the company’s exports had not been affected because it relied on trains to transport 80 percent of its goods and its trucks had been able to enter the port over night.   Cargill said the TEG and TEAG grain and sugar terminals it runs jointly with Louis Dreyfus Commodities were on the Guaruja side of the port and were not affected. Six tanks with a combined capacity of 34,000 cubic meters (214,000 barrels) of ethanol and gasoline were damaged after the fire first broke out on Thursday, Ultracargo said. Shipping agent Williams said that barges were loaded with bunker fuel overnight after state-run oil company Petrobras had resumed deliveries on Tuesday. (Additional reporting by Roberto Samora; Editing by Lisa Von Ahn, Bernard Orr)