More than 10 people in Nanjing, capital city of east China's Jiangsu Province, have been poisoned by the eating of crayfish contaminated with excessive chemical-detergent residue, doctors said Monday.

The people have suffered pain in the back and waist over the past few days, according to doctors at the provincial People's Hospital.

Doctors believe some restaurants used a detergent mainly made of oxalic acid to wash crayfish.

The excessive detergent-residue levels caused rhabdomyolysis, the breakdown of muscle fibers and subsequent release of muscle fiber contents into the blood, which can cause kidney failure or death.

A female patient who only gave her surname, Gong, is still hospitalized.

Gong said she and her mother ate crayfish in the early hours of Aug. 20. They then suffered breathing difficulties and pain in their bodies at about 7:00 AM that day.

Medical checks found 4,000 ug and 6,000 ug of myoglobin -- an iron- and oxygen-binding protein in muscle tissue -- per liter of blood in their respective blood samples, a level much higher than the normal level of 50 ug per liter, said doctor Liu Jia.

(Xinhua News Agency August 24, 2010)