Germany’s Die Welt reports that Iranian authorities are preparing for the possibility that Ali Khamenei’s week-long funeral ceremonies could result in between 1,500 and 3,000 deaths.

Die Welt says the estimate comes from a classified letter involving the Iranian Red Crescent and the country’s National Crisis Management Organisation, sent to First Vice President Mohammad-Reza Aref. The report states officials created contingency plans for a potential mass-casualty disaster during the ceremonies and set up a special unit to manage the dead and missing.

According to Die Welt, thousands of new graves were prepared at Tehran’s Behesht-e Zahra cemetery. A Tehran municipality employee quoted by the paper under a pseudonym for security reasons reportedly said the graves “really exist,” and that authorities had been told that “up to 3,000 dead would be okay,” adding that with “such a large crowd and this extreme heat, no one knows what will happen.”

The report also says it is not independently confirmed. Khamenei’s funeral ceremonies began in Tehran and are expected to continue through Qom, the Iraqi cities of Najaf and Karbala, before Khamenei is due to be buried in Mashhad. Die Welt adds that the authorities are planning a sweeping security and logistical operation in Tehran, including movement restrictions, possible air-travel disruption, large-scale transport, temporary kitchens, and use of schools and mosques to house participants.