A poisoned dog's vomit sent four people to hospital in Colorado.
It is believed the dog ingested rat poison, which, when mixed with water as in a dog's stomach, can produce toxic fumes.
"When the pesticide comes into contact with water, it forms a toxic gas," said inspector Gail McFarland of the Eagle River Fire Protection District, according to the Vail Daily.
"When the dog threw up, this released the gas as the pesticide had mixed with the contents in the dog's stomach."
The dog likely consumed zinc phosphate, a toxic substance used to kill rats.
After the dog vomited four of the clinic's staff began showing signs of respiratory distress and were sent to hospital, said the Daily Mail.
The dog died soon after.
Medical Daily reported that such occurrences are not unusual.
There have been warnings that vet staff should induce vomiting outdoors in the case of poisoning in the future.