Six people working at a parcel delivery service in Amsterdam were hospitalised on Wednesday morning after a package containing the highly dangerous toxin ricin was dropped and a ‘small amount’ of the chemical released, the Telegraaf reports.

The paper says the six members of staff at the GLS delivery firm ‘inhaled’ the vapours and became unwell. They were then taken to hospital for treatment. It is not clear if they have since been released.

Details of how the vial containing the ricin came to break are unclear. However, the accident did not lead to a major alarm with the emergency services and experts in chemical spillages able to stablise and clean up the fluid, the Telegraaf says.

Police experts and the labour inspectorate have been brought in to find out where the vial came from and if health and safety rules were being observed.

Ricin is a highly toxic, naturally occurring substance produced in the seeds of the castor oil plant. A few grains of purified ricin powder can kill an adult.