Oil from China’s drains and gutters treated to look like edible cooking oil in a lucrative night-time operation is being used in “1-in-10” restaurant meals in China.

The swill oil is apparently loaded with aflatoxin.

China Youth Daily reported Wednesday a recent student investigation in Wuhan found 2-3 million tons of ‘swill oil’ makes its way back to rice boxes and meals out each year. It is usually sold as pig feed.

He Dongping, a professor on oil and toxin with central China’s Wuhan Polytechnic University, and also a leading specialist with China’s Food and Oil Standardization Administration, said the conspiracy starts at night when swill-fishers hollow out the stinking hogwash from urban sewages, followed by filtrating, heating, subsiding, dividing, and then in the morning comes out the clear-looking "edible" oil for unwitting customers.

Each fisher could fetch up to four barrels at a time, nearly 300 yuan ($44) easy money every night or over 10,000 yuan ($1,465) a month, a lucrative deal too tempting to resist, especially so when the business was in a trouble-free "anarchy" state,.