This is why I think they are way beyond environmental toxins:
Pathologists, toxicologists and chemists work together during this process, which can involve several rounds of tests. The first tests are basic screens for drugs in the blood and urine, typically using an immunoassay. According to information provided by the CAP, this test utilizes specific antibodies that detect several
classes of drugs such as opiates, amphetamines, marijuana, alcohol and barbiturates. If a drug is detected in the first test, scientists confirm the results by running more tests, which can take several more days and might have to be repeated to ensure accuracy.
A second and more complex test has to be performed if the presence of a drug is confirmed by the first round of tests. The CAP says this test may involve measurements of mass and other characteristics to detect chemicals in substances. This process can take several more days, depending on the complexity of the test and type of drug.
Toxicology Tests and Autopsies - Elite Learning
Much more at link & it’s important to remember that delays more likely mean some type of “toxin” was found and verified by a second lab. Then, the challenging aspect comes, determining precise quantities.
It’s not enough to say someone died from XYZ. The quantity of XYZ must be determined as a fatal amount. Moo. Not implying drugs caused death, only providing info on what tox’ tests involve.
Now, let’s say autopsies led ME/pathologists to a conclusion. They’d then know precisely what to test for. If negative, they’d have to move on to other possibilities. Imo, no way after six weeks is it not clear what caused the 4 deaths. MOO