More than 800 horses have been evacuated and an undetermined number have died as the wildfires sweeping California continue their relentless march southward.

Earlier this week, wildfires devastated more than 180,000 acres in Ventura, Los Angeles, and San Bernardo counties. On Thursday, the blazes moved into San Diego County where fire rapidly approached and swept through the San Luis Rey Downs Training Center, in Bonsall. Caretakers were able to evacuate many horses ahead of the fire’s arrival, but others were turned loose to give them the best chance to avoid the flames when evacuations were no longer feasible. Social media and other published reports suggest that more than 30 horses, many Thoroughbred racehorses, at the training center died.

“We haven’t got a complete head count (of the dead) yet,” said Paul McClellan, DVM, of the San Dieguito Equine Group, in nearby San Marcos.

At the same time, fires threatened homes and boarding barns around the county. McClellan said horse owners and volunteers began evacuating horse from the San Diego County fire zones around 2 p.m