SAN FRANCISCO (KRON) -- On Monday, the Cal Fire Office of the State Fire Marshal announced it completed an investigation into a series of explosions that killed seven workers in a Yolo County fireworks storage warehouse. A barrage of fireworks exploded from the warehouse on July 1, 2025 and ignit ed the "Oakdale Fire" in Esparto, Calif. More than half of the seven victims were San Francisco Bay Area residents who were hired to work at the warehouse. Cal Fire officials revealed Monday that its investigators uncovered evidence of "illegal activities," and sent their report to the Yolo County District Attorney's Office to consider for filing possible criminal charges. "After months of investigation, our Arson and Bomb investigators have compiled a report that reflects the Office of the State Fire Marshal’s commitment to uncovering what happened in Esparto," said California State Fire Marshal Chief Daniel Berlant. "This complex investigation took many turns as new information emerged, but the team diligently followed leads and gathered the facts that form the basis of the report," Berlant said. Officials did not release the Cal Fire investigation report publicly on Monday. According to a civil lawsuit filed last year by a farm located near the warehouse, the fireworks facility was used by a San Francisco-based company, Devasting Pyrotechnics Inc., owned by Kenneth Chee. Chee "operated an unlawful and unpermitted commercial-grade fireworks operation at the fireworks facility," the lawsuit states. Another defendant named in the lawsuit, Yolo County Sheriff's deputy Sam Machado, lived at a residence on the same property. The lawsuit accuses Machado of earning "substantial financial benefits" from allowing an unlawful fireworks operation on the property. Jesus Manaces Ramos, right, and Jhony Ernesto Ramos, left, were killed in the Yolo County fireworks warehouse explosion. (Photos courtesy GoFundMe) The Oakdale Fire burned for six days before investigators could enter the charred disaster zone and recover the seven victims' bodies. A coroner determined that the workers, including a trio of brothers, died from "multiple blast and thermal injuries." The youngest victim, Jesus Manaces Ramos, 18, of San Pablo, was working his first day on the job when the warehouse exploded. Cal Fire's Sonoma-Lake-Napa Unit, local firefighters, and the State Fire Marshal's Arson and Bomb Unit worked together for the months-long investigation. ...read more read less