Sandy Fire Threatens Former Nuclear Lab, Triggering Air Monitoring Around Contaminated Site

SIMI VALLEY, CA — Firefighters made progress controlling the Sandy Fire overnight, reaching 30% containment by Thursday morning, as authorities have paid special attention to a former nuclear research site.

The fire, which has blackened 2,115 acres, broke out around 10:15 a.m. on Monday in a wilderness area abutting a residential neighborhood in the southeastern part of Simi Valley, according to the Ventura County Fire Department.

At least one home was destroyed in the fire.

By Thursday morning the fire was 30% contained, up from 15% 24 hours earlier.

The blaze is burning near the Ventura-Los Angeles county line — north of Calabasas and Agoura Hills and west of the San Fernando Valley — and close to a contaminated site where rocket engines and nuclear reactors were once tested.

#SandyFire Air Quality Update: Due to the Sandy Fire’s proximity to the Santa Susana Field Laboratory area, air quality monitoring is being conducted around the fire perimeter. Monitoring equipment has been proactively deployed to establish background air quality readings and to… pic.twitter.com/zCUGjq3132

— VCFD PIO (@VCFD_PIO) May 21, 2026

"Due to the Sandy Fire’s proximity to the Santa Susana Field Laboratory area, air quality monitoring is being conducted around the fire perimeter. Monitoring equipment has been proactively deployed to establish background air quality readings and to help assess conditions should the fire advance further into the area," fire officials said Wednesday night.

The fire had not crossed into the property at that time, officials said.

Authorities on Wednesday afternoon said they had been making "strong progress" in the overall firefight. "Overall fire activity remains minimal at this time," Cal Fire said.

Firefighters were expecting improved weather conditions Thursday, including lower temperatures and higher humidity, which they expected to assist in the effort to control the blaze, according to the Ventura County Fire Department.

More than 44,000 were under evacuation orders in Ventura County as of Tuesday night. In LA County, residents in parts of Agoura Hills, Calabasas and the far western San Fernando Valley remain under evacuation warnings.

The fire, along with several others burning in the Southland, has negatively impacted air quality.

"Widespread moderate smoke impacts are expected across the LA Basin, Catalina Island, Inland Empire, and Coachella Valley," according to the South Coast Air Quality Management District. "The Sandy Fire is expected to directly impact areas from Simi Valley to (the) San Fernando Valley and out to Arcadia where (the) Air Quality Index may reach the unhealthy for sensitive groups category or higher at times."

City News Service contributed to this report.