Did Cal Fire block Cal-OSHA’s Esparto explosion probe? Here’s what to know

Cal-OSHA investigators were allegedly obstructed by Cal Fire arson and bomb investigators while probing the deadly Esparto fireworks warehouse explosion last year. Sources say the interference delayed the workplace safety investigation.

Here’s our story that detailed the rift between the two agencies. And here are key takeaways:

• The explosion at a warehouse in Esparto storing Devastating Pyrotechnics fireworks killed seven workers on July 1, 2025. Eight people were later indicted by a Yolo County Grand Jury, with five facing murder charges.
• Sources say a four-person Cal Fire arson and bomb unit told witnesses not to speak with Cal-OSHA investigators and withheld documents vital to the workplace safety probe.
• Cal Fire spokesperson Emily Weinzheimer said investigators “initially wanted to ensure all interviews were completed prior to other investigators (OSHA) conducting interviews” to protect the criminal case.
• Attorney Mark Berry said Cal Fire investigator Gershom Slonim told Julian Voller — whose brother Angel, 18, died in the blast — not to attend a July 21 Cal-OSHA interview. Voller was not interviewed until mid-September.
• Maria Melendez, whose husband Joel Melendez Jr. was killed, said Slonim also told her not to speak to Cal-OSHA. “It felt very controlling,” she said.
• Officials said tensions affected the probe to the point that citations would have exceeded the $221,000 assessed if cooperation had been better. Cal-OSHA must complete accident investigations within six months.
• The agencies signed a memorandum of understanding in August to resolve the conflict. Families have filed a $35 million claim against Yolo County and state fireworks regulators alleging negligence.