Greek firefighters planned to continue to work through the night to contain dozens of wildfires, including a massive blaze outside Athens, authorities said. Greek Prime Minister Kostas Karamanlis called for calm on Saturday and said ground forces "will continue their superhuman efforts" until dawn, when air operations and water drops will resume. Authorities reported 75 fires across the country. The fires began late Friday in Grammatiko, 40 kilometers (25 miles) northeast of the capital. Wind whipped a single blaze into three fires, which joined again Saturday. No injuries were reported. Authorities mobilized units from the navy, air force and marines to assist the firefighters in Grammatiko, the state fire department said. "The fire is particularly complex given the weather, the large quantity of fuel, the terrain and the proximity of residential areas," a statement from the fire department said. The cause of the original fire, which belched clouds of heavy dark smoke, was unknown, and officials were investigating. Forest and brush fires are common during Greece's hot, dry summers. Six firefighting aircraft were helping firefighters, according to the Athens News Agency.