BEIJING (Reuters) - Investigators in the northwest Chinese province of Shaanxi have found a radioactive device that was lost earlier this week when a cement plant was dismantled, the official Xinhua news agency said.

The lead ball containing Caesium-137, part of a nuclear scale used to make precise measurements, was lost on Monday as workers disassembled the Qinling Cement Co in Tongchuan, Shaanxi province, Xinhua said.

Investigators, suspecting the ball had been mistakenly sold as scrap metal, found on Friday that it had indeed been melted in a smelter at a local steel plant, Xinhua said. Technicians were now cleaning the contaminated smelter, it said.

Caesium-137 is an extremely toxic radioactive isotope formed through nuclear fission. It can cause cancer years after it is inhaled, eaten or absorbed into the body.

Previous cases of radioactive caesium-137 entering the scrap metal supply from improperly recycled sensors have occurred in Brazil and Spain.

Qinling Cement’s 53-year-old production facilities were dismantled after the plant failed to meet environmental protection standards, Xinhua said.