Founder of CARE organization alleged to have killed healthy dogs to free up space in shelters.
"People believe that heat cures heat, so they eat dog meat and spicy dog soup on the hottest days."
A dozen restaurants in the host county serve dog meat, and only two have take up the government's offer to stop.
The syringes contain enough poison to kill dogs on contact, police said.
Animals Asia reportedly found meat from canines as an ingredient in several items on supermarket shelves.
"It's healthy, just like raising pigs or chickens, it's fine," said one supporter.