I can’t find any report identifying the drug or drugs involved in the mass overdose incident in Chico CA. They were talking about fentanyl or an analog but never anything definite. Another thing about it was I never saw any details about whether anyone in the house was NOT affected. My wild guess was that the victims somehow managed to aerosolize carfentanil, maybe even were trying to make a terror device of that type. The suspicious point was the two police responders were also affected, but now they are trying to explain that away as overreaction by the officers to getting something on their skin:

https://gizmodo.com/police-and-media-keep-spreading-the-myth-that-merely-to-1831777253