Tear gas canisters dumped in a trash bin caused a cloud of white smoke that sickened seven people Thursday near the city hall of a small Washington town, authorities said.
The fumes were released as the canisters were crushed in a garbage truck after the bin was emptied into it, said Snohomish County District 24 Chief Dennis Fenstermaker.
Sheriff's spokeswoman Rebecca Hover said the fumes came from expended tear gas casings belonging to the sheriff's office. The casings were emptied before being thrown away, but some residual gas remained.
The truck driver and six people working nearby suffered irritated eyes, a burning throat and tight chest. They were rushed to Cascade Valley Hospital in Arlington, where they were treated for breathing problems.
Hospital spokeswoman Kelly Penny said the seven people and 11 emergency medical responders had to be decontaminated. All were released, she said.
Fenstermaker said the canisters were improperly disposed.
"They most likely were used in some exercise or something and they placed them in the Dumpster when they thought they were expended," he said. "This may necessitate a change in their disposal practices."
Firefighters with hazardous material training from Everett and Marysville dug into the back of the garbage truck to discover the source of the fumes.
Darrington, a town of 1,900, is about 56 miles northeast of Seattle.