REDMOND, Ore. -- Stomach samples from two dogs recently found dead in Crooked River Ranch will be tested by a state agency to see if they were poisoned.

An officer with the Humane Society of Redmond says eight dogs at the ranch may have been killed or sickened by poison since December.

"I interviewed people in the immediate area who may have seen something suspicious, but people cannot pinpoint where the dogs usually frequent, if it goes here or there," Josh Capeheart, an animal welfare investigator with the society, told KTVZ-TV.

He thinks someone is throwing out strychnine-laced animal parts.

But Michael Odenthal, a pesticide investigator with the Oregon Department of Agriculture, said he suspects the stomach samples to show the dogs ingested a dangerous pesticide called Aldicarb.

"It is a restricted-use pesticide, which means anybody that buys it has to have license and there are records kept of it, so then it narrows it down to who would have access to that type of product," Odenthal said.

The latest victim was Tuffy, an 8-year-old Yorkie who loved to chase birds and went out for the last time Sunday night.

"Yes, I'm convinced he was poisoned," his owner, Rhonda Purdy, told the station. "He was flopping and panting really hard, with his mouth wide open. He passed away within three hours."

A golden retriever who lived near Tuffy had the same symptoms when he died three days earlier.

In an attempt to prevent more deaths, sheriff's deputies in Jefferson and Deschutes counties warned residents this week that they are starting to pick up loose dogs and give out "animal at large" tickets, costing $250.