YINCHUAN - Drug safety regulators in northwest China's Ningxia Hui autonomous region said Friday they are investigating a case in which a company dumped a large quantity of medicine capsules amid a campaign to crack down on the manufacture of chromium-contaminated capsules.

The capsules, totaling more than 500,000, are being tested for excessive levels of chromium, which can be toxic and carcinogenic if ingested in large amounts, said a spokesman with the food and drug bureau of Yinchuan, the regional capital.

On Tuesday, some of the city's residents reported finding a large quantity of green medicine capsules, as well as yellow and white powder, scattered on the side of a road near a residential community in Jinfeng district.

Follow-up investigations showed the capsules were dumped by Ningxia Tianma Pharmaceutical Science & Technology Development Co Ltd, which feared that its weight loss capsules might not be able to pass a safety inspection conducted by local drug regulators, the spokesman said.

The spokesman said local authorities had recovered all the dumped capsules, seized the company's capsule inventory and closed its capsule production lines.

Drug authorities nationwide have been tightening their supervision over the manufacturing and use of capsules after a media report revealed that some Chinese drug makers had packaged several types of medication in capsules made of toxic industrial gelatin.

China Central Television reported on April 15 that 13 commonly prescribed drugs had been packed into capsules made from industrial gelatin, which contains a much greater amount of chromium than edible gelatin.

The Ministry of Public Security has thus far confiscated 77 million capsules made with industrial gelatin.

The ministry has also arrested nine suspects, detained 54 others and shut down 80 illegal capsule manufacturing lines.