Police have arrested 52 suspects who allegedly produced and sold cooking oil recycled from the waste in Jiangxi province, local public security department announced Tuesday.

Gutter oil production?[File photo]?

Since 2010, more than 2,000 tonnes of "crude gutter oil," made from leftover dredged from gutters behind restaurants, were produced by an oil recycling firm in the county of Nanchang, according to police.

Most of the oil was then bought and refined by a Guangdong-based feed-processing company, police said.

The refined "cooking oil" was sold to regional wholesale companies and further distributed to markets and restaurants after being mixed with quality cooking oil and labelled with unregistered trademarks, according to the police.

Police said a total value of 10 million yuan (1.58 million U.S. dollars)was involved in the case.

A further investigation is being conducted.

The case is another crackdown on gutter-oil-producing network that conducts cross-provincial operations.

China launched a nationwide food safety campaign in August, and started to curb the illegal practice of making and selling "gutter oil."

By the end of November, more than 700 suspects had been detained in 128 cases in 28 provinces and municipalities, according to a statement from the Ministry of Public Security issued a week ago.