London, Mar 27 : Chinese officials are urgently seeking a nugget of deadly radioactive material encased in a lead ball of the size of a watermelon that was lost this week.

The Caesium-137 may be buried in a scrap yard under tonnes of metal, and local officials believe it could have been melted down, the BBC reported.

The lead ball was lost when workers at a cement plant tore down an old factory in the north-western Shaanxi Province.

The material was part of a measuring instrument and is extremely toxic. The smallest amount can cause infertility, cancer and even death.

Eight trucks worth of scrap were sold to local steel mills. Tongchuan city officials believe the radioactive material - and its protective container - are likely to have been melted down.

China has an appalling record on industrial safety and there are around 30 cases of radioactive material being lost every year.

In Tongchuan last July a farmer was arrested after he stole a similar radioactive container and attempted to sell it for scrap. (ANI)