In response, Veterinary Public Health carried out site visits to the canals, conducted detailed interviews with dog owners, and reviewed veterinary medical records for reported cases. These efforts helped establish the timeline of symptom onset, identify common exposures, and begin ruling out other potential causes. Alerts were sent to veterinarians across Los Angeles County to raise awareness and encourage the reporting of similar cases. Due to delayed notification, biological samples were available from only three dogs. These were tested for a broad range of potential toxins. While no toxins were detected in these samples, it does not rule them out as a cause of illness, as some toxins are rapidly metabolized, and ideal specimens and post-mortem samples were not available for testing.

On July 30, 2025, the Regional Water Quality Control Board tested the canal water, algae and scum and confirmed the presence of toxins associated with harmful algal blooms (HABs): microcystins, cylindrospermopsin, and anatoxin-a. Based on these findings, the State Water Board and Public Health advised the City of Los Angeles to continue posting HAB warning signs and to conduct biweekly water quality testing until two consecutive tests confirm that cyanobacteria and toxins are below advisory thresholds as outlined in California HAB response guidance.

The investigation also considered other environmental risks, including pesticides. No pesticide misuse was found during the investigation. While a direct link between the dog illnesses and the detected toxins could not be confirmed, HAB exposure remains a possible cause.

Residents and visitors to the affected area are encouraged to follow all posted canal advisories and safety guidance. Whenever and wherever a HAB event is detected, pet owners should prevent their pets from coming into contact with canal water, algae, or shoreline scum. Pet owners who think their pets may be sick should seek immediate veterinary care.