Background: Beginning in 2020–2021, embalmers in multiple countries reported observing large, tough, rubbery white or off-white fibrous structures in the veins and arteries of embalmed corpses, which they described as distinct from classic postmortem clots. Methods: We conducted four annual cross-sectional surveys (2022–2025) of active embalmers in the United States, Canada, United Kingdom, Australia, and New Zealand using SurveyMonkey. A dual distribution strategy (professional associations and direct emails to funeral homes) was used. Core questions assessed observation of unusual white fibrous structures and estimated percentage of corpses affected. Results: Across 808 total responses, the proportion of embalmers reporting observation of these structures ranged from 66% to 83%. Weighted average prevalence in affected corpses ranged from 19% to 27%. The 2022 survey showed a marked increase in first observations beginning in 2020 and accelerating in 2021. Conclusions: Multiple years of surveys document consistent self-reported observations by experienced embalmers of unusual white fibrous structures in a substantial fraction of corpses, with a clear increase noted around 2020–2021. These findings constitute a potential safety signal that warrants independent investigation by forensic pathologists and biomedical researchers to characterize the structures and determine their etiology.