California firefighters aided by aircraft battled a wind-driven wildfire that continued not only burning but spreading early Sunday in an area straddling the San Francisco Bay Area and central California, authorities said.

The Corral Fire began Saturday afternoon near the city of Tracy, 60 miles (96 kilometers) east of San Francisco, and the Lawrence Livermore National Laboratory in the city of Livermore, according to the California Department of Forestry and Fire Protection, or Cal Fire. Dark plumes of smoke traveled high into the sky over the fire area comprised mostly of grassy hills.

Early Sunday, the blaze appeared to be growing, fueled by hot and dry conditions in California. Cal Fire updated the size of the fire to 19.5 square miles (50.5 square kilometers) with 13% contained, up from 17.2 square miles (44.5 square kilometers) late Saturday. Cal Fire said the cause of the fire was under investigation.

Interstate 580, which connects the San Francisco Bay Area to San Joaquin County in central California, was closed in both directions from Corral Hollow Road to Interstate 5 due to the lack of visibility from the smoke, the California Department of Transportation said in a statement.

Cal Fire Santa Clara Unit Chief Baraka Carter said two fire workers were injured, the San Francisco Chronicle reported. The San Joaquin County Office of Emergency Services issued an evacuation order, pinpointing the wildfire in an area east of Interstate 580.

Residents between Corral Hollow Road and Tracy Boulevard were ordered to leave their homes, with residents south of Tracy Boulevard told to be prepared for evacuation.

An evacuation update included areas west of the California Aqueduct south of Corral Hollow Creek, west to Alameda County and south to Stanislaus County. A temporary evacuation point was established at Larch Clover Community Center in Tracy, the county emergency services office said on its website.

Sunday’s high temperature for Tracy was expected to reach 85 degrees Fahrenheit (29 degrees Celsius), with no rain in the forecast, but hotter conditions are on their way.

The National Weather Service said “dangerously hot conditions” with highs of 103 F to 108 F (39.4 C to 42.2 C) were expected later in the week for San Joaquin Valley, an area that encompasses the city of Tracy. Wind gusts of up to 45 mph (72 kph) lashed the region Saturday night, according to meteorologist Idamis Shoemaker of the NWS Sacramento.

The wildfire was near the Lawrence Livermore laboratory’s Site 300 southwest of Tracy, Cal Fire said in a social media post late Saturday.

Lawrence Livermore is a research and development institution primarily focusing on the US nuclear weapons stockpile. Site 300, 15 miles (24 kilometers) east of the laboratory’s main installation, supports “development of explosive materials as well as hydrodynamic testing and diagnostics,” according to the Lawrence Livermore National Laboratory website.

“Here, our researchers can safely formulate, fabricate, and test high-explosive assemblies to assess the performance of nonnuclear weapon prototypes and components,” the website says of Site 300. The wildfire presented no threats to any laboratory facilities or operations and the fire had moved away from the site, Lawrence Livermore spokesperson Paul Rhien said in a statement to The Associated Press early Sunday.

“We have been working in close partnership with Cal Fire, Alameda County Fire Dept, and other emergency services partners throughout the evening,” Rhien said. “As a precaution, we have activated our emergency operations center to monitor the situation through the weekend.”