You can easily induce vomiting in a dog within minutes using hydrogen peroxide. Check your dogs individual dose level requirements on the internet. Obviously the required amount for inducing vomiting in a labrador is much more than in a chihuahua.
I might suggest an alternate theory; it could be someone trying to poison coyotes. There has been talk of vigilantes doing this sort of thing, since they believe the authorities are not doing enough to deal with the perceived problem.
I wondered the same thing last night when I saw this on the news. Is someone trying to bait wildlife like coyotes and way too shortsighted to realize they might kill innocent pets?
