Cat drooling, mewling, and then death?

Tonight our cat went into respiratory distress and died pretty quickly. It started with drooling, which we didn't think was too big a deal (maybe ate something bad). When she started laying still and meowing intermittently, we took her to the 24 hour vet.

By the time we got in there, the following happened pretty rapidly (during exam): Labored breathing, agonal head posture/breathing, slight urination, and finally she deteriorated quickly. We euthanized her just before she died.

The veterinarian did not provide a specific condition, and of course we're not having the cat autopsied. We don't have antifreeze in the garage she was staying in and are struggling to figure out what happened. Does anyone have any idea?

Sounds like she ate something highly toxic to cats. What if she ate a poisonous frog?

Im so sorry for your loss. my condolences. Sounds like she probably ingested some type of poison or could have been bitten by a poisonous spider. Warmest regards.