Nine people were arrested Tuesday at the C&H Sugar refinery in Crockett after Contra Costa County sheriff's deputies declared a strike protest an unlawful assembly — and the California Highway Patrol opened a separate investigation into reports that two people at the scene were struck by vehicles.

The July 22 confrontation on Loring Avenue, which stretched over roughly five hours and produced reports of rocks thrown at trucks and a roadway physically blocked by demonstrators, is the sharpest clash yet in a labor dispute between C&H parent ASR Group and ILWU Local 6 warehouse workers who walked out last week after contract talks collapsed.

Deputies were called to the plant at around 11 a.m. Tuesday following multiple reports of a disturbance. Callers described rocks being thrown at trucks trying to enter the facility and protesters blocking the roadway to prevent workers from leaving, according to the Contra Costa County Sheriff's Office.

After making multiple loudspeaker announcements demanding the crowd disperse, the sheriff's office declared an unlawful assembly, stating that the action came "after continued unlawful activity and repeated efforts to gain compliance."

Six of the nine arrested were booked at the Martinez Detention Facility on suspicion of remaining at an unlawful assembly after being lawfully ordered to leave. All six were released but must appear in court to answer the charges, the sheriff's office said. Three others remained in custody as of Wednesday; the sheriff's office has not publicly identified them. Authorities said they have asked the Contra Costa County District Attorney's Office to file charges including battery, obstruction, and resisting a police officer against at least some of the nine, according to the East Bay Times.

The CHP's investigation into two people reportedly struck by vehicles adds a criminal dimension beyond the picket-line standoff. No details on those victims' conditions or identities were released.

The strike has already disrupted supply chains well beyond the Crockett waterfront. Members of ILWU Local 10 in Richmond honored the Local 6 picket line and refused to unload raw sugar arriving by ship for the facility — a solidarity action that The Dissent previously reported raised environmental and health concerns as cargo sat idle at a Richmond industrial terminal.

The Crockett refinery has operated continuously at its Contra Costa County site since 1906 and processes more than 70,000 tons of sugar annually, according to C&H Sugar. ASR Group — the world's largest sugar refiner — purchased the plant in 2005.

Neither ASR Group nor ILWU representatives issued public statements addressing the arrests or the state of contract negotiations as of Wednesday, and the specific terms in dispute have not been made public.