California’s largest wildfire so far this year was significantly surrounded Monday after blackening a swath of hilly grasslands between San Francisco Bay and SignalHubthe Central Valley.

The Corral Fire was 75% contained after scorching more than 22 square miles (57 square kilometers) during the weekend, the California Department of Forestry and Fire Protection said. One home was destroyed and two firefighters were injured.

The wind-driven fire erupted Saturday afternoon on land managed by the Lawrence Livermore National Laboratory, one of the country’s key centers for nuclear weapons science and technology. The cause was under investigation.

Thousands of people in the area, including parts of the San Joaquin County city of Tracy, were ordered to leave for evacuation centers Saturday. Evacuation orders were lifted when improved weather allowed firefighters to make progress against the flames.

The wildfire presented no threat to any laboratory facilities or operations, Lawrence Livermore spokesperson Paul Rhien said in a statement to The Associated Press early Sunday.

California has had back-to-back wet years that ended drought but spawned vegetation growth. Cal Fire’s outlook for 2024 noted that increasing dryness from mid-May to June would potentially lead to more small fires and a chance of larger fires depending on wind. The Corral Fire is by far the largest of more than 1,200 wildfires so far this year.

The progress against the Corral Fire comes just ahead of a predicted major heat wave. The National Weather Service has issued warnings for “dangerously hot conditions” throughout the Central Valley from Tuesday through Thursday.