An association of eel importers suspended its quality-guarantee system about a month after it was launched in March because a banned antibiotic was detected in frozen eel products from China, the association said Thursday.

The Japan Eel Importers Association decided to suspend its sticker assurance system after enrofloxacin, a synthetic antibiotic for animals, turned up in a number of tests. The substance was believed to have been used at eel farms to prevent illnesses.

The situation has dealt a blow to the eel-importing industry, particularly with the midsummer Day of the Ox, for which nationwide campaigns promoting eel consumption are held, coming up Sunday.