China pupils poisoned with ricin

More than 130 pupils have been treated in hospital in north-west China after eating castor beans - source of the deadly toxin ricin, Xinhua reports.

The students were on a bean-planting trip organised by the provincial youth commission and a local firm, the state news agency said.

It did not list the condition of the students, from Shaanxi province.

One to three castor beans chewed by a child, or just eight seeds chewed by an adult, can be fatal.

Deadly dose

Xinhua said all the other students on the trip in Jingyang County had been checked and no more cases found.

It did not give the pupils' ages but said they were from junior and elementary schools.

Products derived from castor beans include laxatives and soaps.

But they are also the source of the deadly poison.

About 0.2mg of extracted ricin is thought to be the average lethal dose for humans.