Chinese police have arrested 52 people for making and selling cooking oil dredged up from restaurant gutters, state media reported on Tuesday, in the latest food safety scandal to hit the country.

Investigators found that a company in the southern province of Jiangxi had made more than 2,000 tonnes of gutter oil since 2010, which it sold to a feed-processing firm in the neighbouring province of Guangdong, the official Xinhua news agency said.

The oil was then sold to restaurants around the region after being mixed with quality cooking oil and labelled with unregistered trademarks, the report added.

Cooking oil safety scandals have surfaced periodically in China in recent years, and pictures of oil being scooped up from drains have circulated widely online to public revulsion, denting government claims to be addressing food safety problems.

China has struggled to rein in the health safety violations in the unruly and vast food sector despite tough penalties and repeated vows to crack down.

Since July, Chinese courts have sentenced at least a dozen people to jail, including one person who received a suspended death sentence, for their roles in producing or selling pork tainted with toxic chemicals.

In 2008, at least six children died and nearly 300,000 fell ill from drinking milk laced with melamine powder, an industrial compound added to milk to give misleadingly high results in protein tests.

(Reporting by Sally Huang and Ben Blanchard; Editing by Ken Wills)