Police have detained nine more people at two gelatin plants that supplied toxic industrial gelatin to drug capsule producers, local authorities said on Wednesday.

Police in east China's Zhejiang province previously detained 23 people who allegedly produced and sold pharmaceutical capsules made from industrial gelatin, which contains excessive levels of chromium.

Seven of the nine newly-announced detainees worked at the Xueyang Glair Gelatin Factory located in Fucheng county in the northern province of Hebei, according to a Wednesday statement from the county's food safety office.

The factory's owner Song Xunjie was detained on Monday for arson, as he allegedly set fire to his plant to destroy evidence following a Sunday report by China Central Television (CCTV) in which it was alleged that his plant provided industrial gelatin to a capsule producer in Zhejiang.

Authorities have suspended production at the factory and sealed 200 tonnes of gelatin for further analysis.

The other two suspects worked at the Guifeng Gelatin Company in Yiyang county of Jiangxi province. The company allegedly sold industrial gelatin labeled as edible gelatin to capsule producers, the county government's information office said in a statement released on Wednesday.

Another five employees of the company are being monitored by the police, said the statement.

A director of a quality inspection bureau in Yiyang has also suspended from post amid the scandal, it said.

The State Food and Drug Administration (SFDA) issued an emergency notice Sunday halting the sale and consumption of 13 kinds of drugs packed in capsules that have been confirmed to contain excessive levels of chromium.

Chromium is a carcinogen used in a variety of industrial manufacturing processes.

The SFDA said it has ordered its provincial-level bureaus to follow up on the case.