JACKSON -- An apparent spill of the mosquito pesticide malathion killed some 300 brown trout and whitefish in the Green River last week just north of Daniel in Sublette County.

The spill is thought to have come from a plane spraying for mosquitos last Tuesday or Wednesday.

Brian Lovett, inspection and compliance program officer for the Wyoming Department of Environmental Quality, said there were reports of a spray plane with leaking problems at the Pinedale airport around the time of the spill.

Lovett was in the area over the weekend collecting samples. It has not been confirmed that the pollutant causing white congealed globs in the river was malathion, but Lovett said the smell indicated it was.

The samples, collected from the site of the spill and downstream, will be run in the state Department of Agriculture laboratory this week.

Lovett said the spill should not cause a human health hazard.

"What's there now seems to be staying where it is," he said. "It's material that breaks down fairly rapidly. My guess is that the fish kill was probably instantaneous when the spill occurred."

Lovett said there is a malathion product called "ultra low volume" that is a concentrate and is sprayed in a fine mist at the volume of about 8 ounces per acre.

"I would guess what happened was he had an equipment malfunction over the river," Lovett said. "There's a 200-yard stretch that had this material in it."

Lovett added he was guessing, as a confirmation of the pollutant was pending.

The pollutant and fish kill was reported to the Wyoming Game and Fish Department by an angler Friday. Officials went to the site and on Saturday began cleaning the area using turkey basters to siphon the globules out of the river. Not all of the material was removed.

Lovett said DEQ is working to determine whether to clean it up, or if it will dissolve.

"We're kind of sorting it all out," he said Monday.

Lyndsay Griffin, public information officer with the Department of Agriculture, said it will be up to DEQ to determine what to do about the spill. The Department of Ag licenses the commercial applicators in the state and is working to determine exactly what happened.

Griffin said it is still not known what the pollutant was, but signs indicate it was malathion based on the smell and characteristics.

"As far as we know now, the chemical has some pretty drastic initial consequences, but it dissipates pretty quickly," she said. "There are no long-term effects."

Hank Uhden, manager of the Department of Ag's technical services division, said until the agency gets on site and does the investigation it is hard to say what happened, but it's possible it was from a leaky plane.

He said this is an isolated incident.

Environmental reporter Whitney Royster can be reached at (307) 734-0260 or at royster@tribcsp.com.