A batch of phytosanitary products was placed under supervision in an agro-pharmaceutical plant after it was noted that 300 t of mancozebe in big-bags intended for shipment to a company in the Rhone region. Having noted that the heating phenomenon had continued the following day, the operator contacted the customer, informing them that they should monitor the last big-bags delivered. The latter had also noted the self-warming phenomena and the progressive increase in temperature (see ARIA No. 32277), and decided to initiate the establishment’s internal contingency plan and flood the batch by placing it in tanks of water. The big-bags still at the supplier’s site were isolated in a special location and monitored. The manufacturer recovered the batch that had been treated on the customer’s premises for progressive recycling. Analyses and tests determined that the self-heating phenomenon was the result of recent modification in the packaging process at the customer’s request. The product’s decomposition was promoted by the product’s increased contact with the air. The customer decided to return to the initial packaging. Manufacturing operations resumed after several days.