Police in Sao Paulo have recovered a shipment of radioactive material four days after armed robbers stole it. The cargo was found in a vacant lot.

The material, the isotope Actinium-225, arrived from the United States through Guarulhos airport. It was headed to a hospital that treats cancer patients. During the journey, four armed men stopped the van, stole it and held the driver hostage overnight.

The van was later found destroyed in Ferraz de Vasconcelos, without the cargo. Acting on an anonymous tip, civil police found the material in a vacant lot in Parque Sao Rafael, in Sao Paulo’s east zone. Officers were told not to touch it until specialists arrived. The manufacturer confirmed the cargo and it was returned to the transport company.

Actinium-225 is used in targeted cancer treatment. Authorities warned that anyone who finds packages marked as radioactive must not touch them and should call the police at once.

The National Nuclear Energy Commission is monitoring the investigation. Police are still looking for the robbers.