An anonymous tip led to the discovery that 10 college students, aged between 18 and 22, had gathered for a late night hangout at an abandoned property where the fire originated, Santa Barbara County Sheriff Bill Brown said. He declined to say which college the students attended.

“It appears this fire was the result of carelessness, not criminal intent,” Brown said.

No criminal charges have been filed, but the county district attorney will review the case, Brown said.

The fire consumed nearly 2,000 acres (800 hectares) in Santa Barbara County and critically injured a couple who were burned as they fled their home, which was destroyed by the flames. The college group left the smoldering bonfire in the middle of the night and the embers sparked the wildfire 13 to 14 hours later, Brown said. The group had been hanging out at a property known locally as the “tea garden” next to an abandoned tea house in the hills of Montecito. “They thought the fire was extinguished, but we don’t have a lot of detail to disclose about what they did to do so,” Brown said.

The fire was the first of three blazes to erupt in Southern California in the last week which have collectively damaged or destroyed about 1,000 homes and blackened more than 65 square miles (168 square kilometers).

In Southern California, the Santa Ana winds that swept six counties like a blowtorch died down Tuesday, allowing crews to mop up the smoldering hotspots.

The 11,234-acre (4,546-hectare) fire in the San Fernando Valley was 85 percent contained; About 50 miles (80 kilometers) to the south, the last remaining evacuation order was lifted in Orange County, where a nearly 29,000-acre (11,736-hectare) complex of fires was 90 percent contained and some of the 3,760 firefighters were being sent home.