Insecticides killed a fisher found at a marijuana grow in late July, the Humboldt County Sheriff's Office reports.

A necropsy determined the mammal — a candidate for the endangered species list — was killed by Methomyl, an insecticide, and had rodenticide in its system as well. 

From the Sheriff's Office:

The necropsy of the deceased young male adult Fisher located in the marijuana garden in Six Rivers National Forest on 07-31-2013 was recently completed by a scientific team of researchers. The necropsy confirmed suspicions that the Fisher was in fact killed due to Carbamate insecticide poisoning, specifically Methomyl. Methomyl is a highly acute toxic insecticide, its use restricted by the United States Environmental Protection Agency. The Fisher also had Brodifacoum a 2nd generation anticoagulant rodenticide detected in its system. The researchers believe the Fisher experienced convulsions, muscle tremors and respiratory distress during its death. 
There were pieces of meat believed to be hotdog inside the Fishers stomach. It was pointed out that if this hotdog were eaten by any other animal it would be toxic to that animal and this toxicant can travel through the food chain, so any scavenger eating an animal poisoned with this would also likely become ill or die.

The researchers believe this is also a public safety issue. See below from Cornell University:

Methomyl is potentially a highly poisonous material in humans (6). It is highly toxic if it is ingested or absorbed through the eyes, moderately poisonous when inhaled, but of lower toxicity with skin, or 'dermal,' exposure (18, 30). Methomyl is a highly toxic inhibitor of cholinesterase, an essential nervous system enzyme. Symptoms of anti- cholinesterase activity include weakness, blurred vision, headache, nausea, abdominal cramps, chest discomfort, constriction of pupils, sweating, muscle tremors, and decreased pulse. If there is severe poisoning, symptoms of twitching, giddiness, confusion, muscle incoordination, slurred speech, low blood pressure, heart irregularities, and loss of reflexes may also be experienced. Death can result from discontinued breathing, paralysis of muscles of the respiratory system, intense constriction of the openings of the lung, or all three (6, 16). The onset of symptoms may be delayed up to 12 hours (16). The route, duration, and concentration of methomyl exposure will affect the severity of poisoning and the number and types of symptoms that occur. Complete recovery from an acute poisoning by methomyl, with no long term health effects, is possible if exposure ceases and the victim has time to reform their normal level of cholinesterase and to recover from symptoms (7, 26). (For more information on cholinesterase, please refer to the Toxicology Information Brief on Cholinesterase- Inhibition).

The public is being advised to not handle or touch any items located in any active or inactive marijuana garden site. The items in the site could potentially poison the person by the mere handling of the items; some of these chemicals can travel through exposed skin. Allowing your dog off leash in areas where one of these grows is located could also result in your dog being poisoned. If marijuana grow site is located leave the area immediately and notify local law enforcement.

Results of the necropsy are available  here .