(CNN)  -- A wildfire continued its rampage through the San Bernardino National Forest in Southern California on Monday, but the U.S. Forest Service said fire crews were gaining ground.



The Sheep Fire in Southern California has burned thousands of acres and left this bus a charred ruin.



"Firefighters have made very good progress against the Sheep Fire. It's currently at approximately 7,500 acres with 20 percent containment," U.S. Forest Service spokeswoman Robin Prince said Monday.



The fire, which was reported Saturday afternoon in the Lytle Creek area, quickly grew to 3,500 acres by early Sunday and forced about 4,000 people in the community of Wrightwood from their homes.



"People are going to have to hold off on getting back to their homes until we get a little better containment lines on the fire, but things are looking really good," according to Prince.



More than 1,200 firefighters were battling the blaze, and numerous firefighting aircraft have dropped water and retardant on the wildfire. Back fires have been set to protect homes at the eastern edge of Wrightwood, authorities said.



The weather was cooperating Monday, unlike over the weekend when a high-wind warning remained in effect and gusty winds helped fan the flames.



"There's very little smoke. There's a few flare ups here and there, but if the winds pick up, we could still have some problems. So that's why we're holding off on letting people go back into the mandatory evacuated area," said Prince.



California Gov. Arnold Schwarzenegger declared a state of emergency in San Bernardino County on Sunday so the state can mobilize agencies and equipment to help fight the fire.
How many people were forced out? How many acres? What is the containment range? People aren't being allowed to return to what? The Sheep Fire covers how much ground? How many people in San Bernardino County have been forced from their homes? What was the count of people that had to leave San Bernardino County? What was the size of the Sheep Fire?
4,000 7,500 20 percent go back into the mandatory evacuated area," approximately 7,500 acres about 4,000 about 4,000 approximately 7,500 acres with 20 percent containment,"
question: How many people were forced out?, answer: 4,000 | question: How many acres?, answer: 7,500 | question: What is the containment range?, answer: 20 percent | question: People aren't being allowed to return to what?, answer: go back into the mandatory evacuated area," | question: The Sheep Fire covers how much ground?, answer: approximately 7,500 acres | question: How many people in San Bernardino County have been forced from their homes?, answer: about 4,000 | question: What was the count of people that had to leave San Bernardino County?, answer: about 4,000 | question: What was the size of the Sheep Fire?, answer: approximately 7,500 acres with 20 percent containment,"